Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link: http://www.jett.dormaj.com  
Analysis of Suitable Signal Peptides for Designing  
a Secretory Thermostable Cyanide Degrading  
Nitrilase: An in Silico Approach  
1
1
2
3,4  
Marzieh Asadi , Saba Gharibi , Seyyed Hossein Khatami , Zahra Shabaninejad ,  
1,4*  
Farzaneh Kargar , Fatemeh Yousefi , Mortaza Taheri-Anganeh *, Amir Savardashtaki  
1
5
1
1
- Department of Medical Biotechnology, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical  
Sciences Shiraz, Iran  
2
- Recombinant Proteins Laboratory, Department of Biochemistry, School of Medicine, Shiraz University of Medical Sciences,  
Shiraz, Iran  
3
- Department of Nanobiotechnology, School of Basic Sciences, Tarbiat Modares University, Tehran, Iran  
- Pharmaceutical Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran  
- Department of Biological Sciences, Faculty of genetics, Tarbiat Modares University, Tehran, Iran  
4
5
Received: 17/05/2019  
Accepted: 24/08/2019  
Published: 26/08/2019  
Abstract  
Secretory production of recombinant proteins has many benefits such as solubility and ease of purification. The aim of this  
study was to find suitable signal peptides for secretory production of nitriles in Bacillus subtilis. The signal peptides were chosen  
from Signalpeptide web server. SignalP server was used to define probability of suitable signal peptides and their secretion  
pathways. Physico-chemical properties and solubility were predicted by ProtParam and Protein-sol, respectively. Bioinformatics  
analysis identified SUBF_BACSU, GUB_BACSU, SACB_BACAM and AMY_BACAM that linked to nitriles are appropriate  
signal peptides. Their fusion proteins could be stable, soluble and non-antigenic proteins that might have suitable secondary and  
tertiary structures. The recommended signal peptides by this study are appropriate for rational designing of secretory soluble  
nitriles. Thus, the results of present work can be useful for future experimental production of secretory and soluble nitriles.  
Keywords: In silico, Nitrilase, Cyanide, Signal Peptide.  
1
from cytochrome c to oxygen. As a result, it affects the  
1
Introduction  
cellular use of oxygen and oxidative metabolism (5-7). The  
organs which are mainly affected by cyanide poisoning are  
the central nervous system and heart (8, 9). Although  
conventional methods for treatments of cyanide  
wastewaters such as chemical and physical treatments  
efficiently can decrease the toxicity from cyanide, they  
involve high cost of construction and engineering, long-  
term storage, and require reagents that can be harmfulto the  
environment (10, 11). Undertaking biological processes for  
cyanide degradation is the best alternatives and approaches  
to overcome these problems (12, 13). Cyanides removal by  
Polluted water and soil are major environmental  
problems. Use of pesticides, fossil fuels, fertilizers, mining,  
municipal wastes, and sewage are the main cause of this  
pollution (1). Sewage from industrial wastewater and  
agricultural processing can hold a considerable amount of  
potential pollutants, including organisms/pathogens, trace  
organic chemicals and toxic compounds, such as cyanides,  
sulphates, phenols, and metals, etc.)3 ,2(. Cyanide  
compounds can be highly toxic to many life forms and are  
available in the form of nitriles, cyanides, and carbonitriles  
(
4). Cyanide can bind to the enzyme cytochrome c  
oxidase and inhibit the transportation of electrons  
biodegradation  
process  
includes  
utilizing  
the  
microorganisms and plants which have the various enzymes  
in their systems, and able to converting cyanides to non-  
toxic compounds (13, 14). Using these methods are  
efficient, cost-effective, and have a faster rate compare to  
conventional ones (15). Nitrilases are the enzymes related  
to the group of hydrolases that convert the nitrile (R-CN)  
compounds into their corresponding carboxylic acids and  
ammonia using a simple hydrolytic pathway. They are  
widely found in nature and can be isolated from microbes  
Corresponding author: Dr. Amir Savardashtaki, (a)  
Department of Medical Biotechnology, School of  
Advanced Medical Sciences and Technologies, Shiraz  
University of Medical Sciences Shiraz, Iran. (b)  
Pharmaceutical Sciences Research Center, Shiraz  
University of Medical Sciences, Shiraz, Iran. E-mail:  
dashtaki63@gmail.com.  
5
06  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
and plants (16, 17). Nitrilases have been acknowledged as  
valuable biocatalysts in the protection of the environment  
due to their capability to convert cyanide to non-toxic  
products (18). Bacteria are broadly used as cell factories  
with the aim of recombinant proteins production. Its request  
in biotechnology has increased dramatically with every  
passing day, as it represents a multi-billion-dollar market  
through its application such as technical bulk enzymes and  
biopharmaceutical proteins (19). Most of its applications  
include complex proteins are challenging to produce thus in  
2
Methods  
2
.1 Dataset retrieval  
The amino acid sequences of 30 SPs peptides were  
retrieved from database resources, “Signal Peptide  
http://www.uniprot.org) were employed to confirmed  
selected signal peptides data according to the experimental  
evidence. The key factors of collecting the data for the  
following steps were the ones belonged to bacterial  
secretory proteins and mentioned in previous studies.  
Retrieved sequences are listed in Table 1.  
production of  
a successful recombinant protein the  
important consideration is the choice of a proper expression  
system and also the host’s potential for the secretion of  
heterologous proteins since it is critical to provide an active  
and stable protein (20). High-level expression of  
heterolegus proteins can lead in accumulation of insoluble  
misfolded proteins in the cytoplasm, which is identified as  
the inclusion bodies. These aggregated intermediates can  
not have a suitable biological activity. As a result, one  
important step in production of recombinant protoein is to  
refolded the inclusion bodies to to get the applicable  
soluble proteins (21). The gram-negative Escherichia coli  
2
.2 Prediction of signal peptides presence, their cleavage  
site location and Secretion pathway  
SignalP with an accuracy of 87% (35) is an artificial neural  
network (ANN) based tool and is categorized among the  
most accurate and reliable tools in all proposed data mining  
models for prediction of the SPs sequences and their  
was employed to identify the signal peptide probability and  
their precise cleavage sites together with their secretion  
pathway. Sequences with probability value greater than 0.5,  
were introduced as competent signal peptides for next  
section analysis.  
(
E. coli) and the gram-positive Bacillus subtilis (B. subtilis)  
are the favourite hosts for producing the vast majority of  
recombinant proteins (22, 23). E. coli has several  
advantages for heterologous protein expression, such as  
easy growth on inexpensive media and rapid biomass  
accumulation in a short fermentation period (24-26).  
However, there is some limitation in using this organism, as  
recombinant proteins in E. coli can express in the form of  
inclusion bodies and incorrect protein folding while, B.  
subtilis has many outstanding features. It is non-pathogenic  
and endotoxin-free organism (27, 28) and has a great  
protein secretory capability as they can secrete proteins  
directly and efficiently into the cultural medium via the Sec  
and Tat pathway (27). Furthermore, their outstanding  
biochemical and physiological features make them easy for  
experiment handling and genetic manipulation (29).  
Another characteristic of B. subtilis that makes it a more  
suitable host for the production of secretory heterologous  
protein is its lack of outer membrane (30, 31). Therefore,  
they can be applied for the efficient production of large-  
scale industrial enzymes, proteins, and antibiotics. In  
addition to B. subtilis potential for the secretion of  
recombinant proteins, the signal peptides (SPs) that direct  
the export proteins into the general secretory pathway are  
important. SPs can improve the protein folding, solubility  
of recombinant proteins, and reduces the purification  
process. (32). SPs are normally short (15 to 30 amino acids  
long) and share a common triplex structure including a  
positively charged amino-terminal region (n-region), a  
hydrophobic region (h-region) and a cleavable site (c-  
region). N and h-region have a role in channelling the  
recombinant proteins into periplasmic space. C-region as a  
cleavage site location is important as it can be recognized  
by signal peptidase enzyme (33, 34). This study aimed to  
comparedesigning computationally the several signal  
peptides with respect to their amino acid composition and  
their physico-chemical properties in order to investigate  
and select suitable candidates for secretory production of  
nitrilase in the B. subtilis host.  
2
.3. Evaluation of signal peptides physico-chemical  
properties and solubility  
online  
software  
http://web.expasy.org/protparam/) (37), was utilized for in  
silico prediction of the diverse physico-chemical features of  
the recorded signal peptides, containing amino acid  
composition, GRAVY (grand average of hydropathicity),  
aliphatic index, molecular weight (MW), theoretical  
isoelectric point (pI), positively and negatively charged  
residues and instability index on SPs linked to nitrilase (37,  
3
8). Prediction of protein solubility was done by online  
sol.manchester.ac.uk). This server provides a solubility  
score between 0-1 to make interpreting the results  
simpler(39). For the final analysis, unstable fusion proteins  
were removed and the SPs representing a solubility higher  
than 0.45 selected.  
2
.4. In silico prediction of signal peptides secretion  
pathway and sub-cellular localization  
Searches for Sub-cellular localization of different signal  
peptide infusion with nitrilase and their final destination  
were performed using an online tool “ProtCompB”  
(
http://www.softberry.com). The Softberry prediction is based  
on neural networks and reports between 86100% correct  
prediction (40-42).  
3
3
Result  
.1 Selection of signal peptides and sequence definition  
A total number of 30 prokaryotic signal peptides was  
selected from several different Gram-positive and Gram-  
negative bacteria and their primary structure was retrieved  
from online server which are listed in Table 1.  
5
07  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
Table 1: Amino acid sequences of the signal peptides.  
Accession No. Signal Peptide  
Protein Name  
Source  
Amino Acid Sequence  
1
2
3
4
MVKSFRMKALIAGAAVAAAVSAGAVSDVP  
5
6
7
8
9
MAYDSRFDEWVQKLKEESFQNNTFDRRKFIQ  
1
0
1
1
1
2
MMKMEGIALKKRLSWISVCLLVLVSAAGM  
1
3
Bacillus amyloliquefaciens  
1
1
1
4
5
6
Bacillus amyloliquefaciens  
Bacillus amyloliquefaciens  
Bacillus amyloliquefaciens  
MIQKRKRTVSFRLVLMCTLLFVSLPITKTSA  
1
1
7
8
Bacillus stearothermophilus  
Bacillus stearothermophilus  
MRRWLSLVLSMSFVFSAIFIVSDTQKVTVEA  
1
2
2
9
0
1
Q5ZF24  
P23550  
Q5ZF24_LACSK  
GUNB_PAELA  
n/a  
Bacillus stearothermophilus  
Lactobacillus sakei  
MQNTKELSVVELQQILGG  
Endoglucanase B  
Paenibacillus lautus  
MKKRRSSKVILSLAIVVALLAAVEPNAALA  
2
2
Q93MG8  
n/a  
Thiobacillus ferrodoxin  
MFKRLANAAIPFALVGMLFGLSVSVASA  
MSEKDKMITRRDALRNIAVVVGSVATTTMM  
GVGVADA  
MYTQNTMKKNWYVTVGAAAALAATVGMG  
TAMA  
MTTYLSQDRLRNKENDTMTYQHSKMYQSRT  
FLLFSALLLVAGQASAA  
2
2
3
4
P50500  
P24930  
IRO_THIFE  
Iron oxidase  
Rusticyanin  
Thiobacillus ferrodoxin  
Thiobacillus ferrodoxin  
Thiobacillus ferrodoxin  
RUS2_THIFE  
2
2
2
5
6
7
P74917  
P45741  
P21543  
CY552_THIFE  
THI1_PANTH  
AMYB_PAEPO  
Cytochrome c-552  
Thiaminase-1  
Paenibacillus thiaminolyticus MSKVKGFIYKPLMVMLALLLVVVSPAGAG  
MTLYRSLWKKGCMLLLSLVLSLTAFIGSPSNT  
ASA  
Beta/alpha-amylase  
Paenibacillus polymyxa  
Arabinoxylan  
2
2
3
8
9
0
P45796  
P31835  
P04830  
XYND_PAEPO  
CDGT2_PAEMA  
CDGT1_PAEMA  
Paenibacillus polymyxa  
Paenibacillus macerans  
Paenibacillus macerans  
MIRKCLVLFLSFALLLSVFPMLNVDA  
MKKQVKWLTSVSMSVGIALGAALPVWA  
MKSRYKRLTSLALSLSMALGISLPAWA  
arabinofuranohydrolase  
Cyclomaltodextrin  
glucanotransferase  
Cyclomaltodextrin  
glucanotransferase  
The amino acids in the n-region are shown in boldface and the underlined amino acids represent the c-region.  
3
.2 Signal Peptide prediction by SignalP-5.0 Server  
Based on the SignalP result, SPs with probability below  
.5 were excluded from this analysis since signal peptidase  
QOX2_BACSU, RNBR_BACAM and Q5ZF24_LACSK  
were under the cut-off value.  
0
might not identify their cleavage site. The probability  
3.3 Physico-chemical properties and solubility  
ProtParam results as shown in Table 3. The length of  
all signal peptides were in the range of 21 to 47 amino  
5
08  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
acids and net positive charge in the n-region was between 1  
the high expression levels of recombinant proteins, protein  
secretion can be a solution and for secretion through above  
mentioned pathways, an appropriate SP selection is an  
essential step. Therefore, the SPs have a key role in  
directing the protein into the periplasmic space and out of  
cell (43).  
Computational tools are being used in the large variety  
of eras in medical and biological fields. Using  
bioinformatics tools helps to reduce the cost of experiments  
and provide more accurate and validate outcomes (44, 45).  
In this study, several different signal peptides were  
evaluated and a total number of prokaryotic SPs from  
different organisms with the acceptable efficiency in the  
previous studies were selected. For a successful secretion,  
various features should be balanced during the secretory  
pathway. The physicochemical and structural features of a  
signal peptide are important properties that should be  
carefully considered. Therefore, different computational  
methods have been applied to predict the physicochemical  
properties of the SPs.  
The highest aliphatic index belonged to  
CWBA_BACSU (160.00), XYND_PAEPO (161.15) and  
GUNB_PAELA (153.00). XYND_PAEPO (1.669),  
CWBA_BACSU (1.596) and GUB_BACAM (1.508) had  
the highest GRAVY. Based on instability and solubility  
results, nitrilase fused with all SPs were predicted to be  
stable and soluble.  
3
.4 In silico prediction of signal peptides sub-cellular  
localization  
translocate nitrilase into extracellular space. So other SPs  
were excluded in this study (Table 4).  
4
Discussion  
Nitrilase, as a monomeric protein and lacks disulfide  
bonds, looks to be a suitable candidate for secretory  
production in prokaryote hosts like Bacillus subtilis. Sec,  
SRP, and TAT are pathways that are recruited by  
prokaryotes. Considering the problem of creating high  
amounts of inclusion bodies, aggregation and misfolding in  
Table 2: Signal Peptide Probability, Cleavage Site and Secretion pathway  
No.  
1
Probability  
0.58  
0.15  
0.51  
0.70  
0.26  
0.76  
-
Cleavage site  
AAA-AM (28,29)  
-
Secretion pathway  
(Sec/SPI)  
-
2
3
AGA-MV (30,31)  
SFA-MV (25,26)  
-
(Sec/SPI)  
(Sec/SPI)  
-
4
5
6
ADA-MV (27,28)  
-
(Sec/SPI)  
-
7
8
0.80  
0.91  
0.44  
-
ANA-MV (21,22)  
AEA-MV (26,27)  
-
(Sec/SPI)  
(Sec/SPI)  
-
9
Q5ZF24_LACSK  
GUNB_PAELA  
Q93MG8_THIFE  
IRO_THIFE  
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
-
-
0.69  
0.07  
0.78  
0.75  
0.56  
0.89  
0.64  
0.76  
-
ASA-MV (28,29)  
-
(Sec/SPI)  
-
AFA-MV (29,30)  
TSA-MV (31,32)  
VSA-MV (25,26)  
VKA-MV (30,31)  
VEA-MV (31,32)  
ASA-MV (25,26)  
-
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
-
0.79  
0.69  
0.73  
0.63  
0.55  
0.60  
0.82  
0.86  
0.73  
0.84  
ALA-MV (30,31)  
ASA-MV (28,29)  
ADA-MV (37,38)  
AMA-MV (32,33)  
ASA-AM (46,47)  
AGA-GM (28,29)  
ASA-MV (35,36)  
VDA-MV (26,27)  
VWA-MV (27,28)  
AWA-MV (27,28)  
(Sec/SPI)  
(Sec/SPI)  
(Tat/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
(Sec/SPI)  
RUS2_THIFE  
CY552_THIFE  
THI1_PANTH  
AMYB_PAEPO  
XYND_PAEPO  
CDGT2_PAEMA  
CDGT1_PAEMA  
5
09  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
Table 3: Physico-chemical properties and solubility and Final prediction site of signal peptides  
Amino  
Aliphatic  
Instability Index  
Without protein  
unstable  
Instability index  
with protein  
stable  
Solubility  
(Probability)  
No.  
1
Signal peptide  
Net Charge  
GRAVY  
0.752  
acids  
Index  
1
1
1
1
1
1
1
1
1
1
9
1
1
1
41.72  
17.00  
60.00  
19.63  
11.90  
16.54  
42.86  
07.93  
19.35  
48.00  
1.00  
29  
30  
25  
27  
21  
26  
28  
29  
31  
25  
30  
31  
25  
30  
4
5
2
1
2
2
2
3
6
2
5
1
2
4
Soluble(0.540)  
Soluble(0.558)  
Soluble(0.533)  
Soluble(0.548)  
Soluble(0.575)  
Soluble(0.582)  
Soluble(0.567)  
Soluble(0.564)  
Soluble(0.533)  
Soluble(0.545)  
Soluble(0.476)  
Soluble(0.528)  
Soluble(0.576)  
Soluble(0.585)  
(
50.51)  
stable  
20.75)  
unstable  
42.97)  
stable  
31.87)  
stable  
10.61)  
stable  
0.70)  
unstable  
40.54)  
stable  
26.18)  
unstable  
47.44)  
unstable  
45.44)  
unstable  
86.84)  
unstable  
46.86)  
stable  
33.02)  
unstable  
67.87)  
stable  
18.74)  
unstable  
61.56)  
stable  
-3.23)  
unstable  
51.76)  
stable  
34.22)  
unstable  
45.90)  
stable  
15.75)  
stable  
34.65)  
stable  
36.17)  
(30.42)  
stable  
(27.43)  
stable  
(29.48)  
stable  
(28.54)  
stable  
(26.89)  
stable  
(25.71)  
stable  
(29.39)  
stable  
(28.00)  
stable  
(30.23)  
stable  
(29.70)  
stable  
(34.22)  
0.497  
1.596  
1.122  
0.948  
0.769  
1.443  
0.710  
0.606  
1.508  
0.117  
0.887  
1.100  
0.920  
2
(
3
(
4
(
5
(
6
GUNB_PAELA  
(
7
(
8
(
9
(
1
1
1
1
1
0
1
2
3
4
(
(
16.13  
21.60  
53.00  
stable  
(30.17)  
stable  
(28.62)  
stable  
(
(
(
(32.27)  
1
22.14  
1.379  
stable  
(27.28)  
1
5
28  
2
Soluble(0.572)  
(
9
6
7
1
1
1
1
1
2.16  
0.276  
0.372  
-0.355  
1.359  
0.751  
1.669  
0.785  
0.467  
stable  
(32.33)  
stable  
(24.78)  
stable  
(31.78)  
stable  
(28.80)  
stable  
(30.28)  
stable  
(27.07)  
stable  
(28.80)  
stable  
1
1
1
1
2
2
2
2
6
7
8
9
0
1
2
3
IRO_THIFE  
37  
32  
47  
29  
35  
26  
27  
27  
1
2
2
3
3
1
3
4
Soluble(0.549)  
Soluble(0.541)  
Soluble(0.488)  
Soluble(0.575)  
Soluble(0.500)  
Soluble(0.549)  
Soluble(0.536)  
Soluble(0.541)  
(
4.38  
RUS2_THIFE  
(
4.89  
CY552_THIFE  
THI1_PANTH  
AMYB_PAEPO  
XYND_PAEPO  
CDGT2_PAEMA  
CDGT1_PAEMA  
(
41.03  
17.14  
61.15  
15.56  
15.93  
(
(
(
(
(
(28.94)  
A critical step in designing constructs for secretory  
production of the recombinant proteins is the exact  
prediction of the cleavage sites located in the signal  
peptide. For this purpose, the SignalP server was employed  
and the probability was considered as the most important  
parameter to identify SPs. According to the default cutoff  
value of 0.5, SPs with cut-off value > 0.5 was identified as  
potential SPs for nitrilase (46).  
SignalP can distinguish appropriate and non-  
appropriate sequences for secretory protein production.  
Based on the results of SignalP analysis, the cleavage sites  
of BLAC_BACLI, YXAL_BACSU, AMY_BACSU,  
PPBD_BACSU, QOX2_BACSU, RNBR_BACAM, and  
Q5ZF24_LACSK signal peptides infusion with nitrilase  
cannot properly recognize by signal peptidase.  
Consequently, they are not recognized as potential choices  
for nitrilase secretion and were disregarded from further  
analysis. According to SignalP (Table 2), 23 out of 30  
collected SPs were identified as proper SPs for nitrilase.  
However, more characteristics were required to select  
appropriate SPs.  
Data aslo were compared according to the key  
physicochemical features of the signal peptides including  
net positive charge, GRAVY, instability and aliphatic  
indexes by ProtParam server (Table 3). GRAVY and  
Aliphatic index are the two factors which are directly  
associated with hydrophobicity (22) and improving the  
level of this parameter and length of the h-region, leads to  
5
10  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
improve the rate of the protein secretion. (47). As shown in  
Table 3, all 23 listed SPs in this step, had suitable aliphatic  
indexes and hydrophobicity for secretion.  
subcellular localization of SPs infusion with nitliase. It was  
elucidated that among 23 stable and soluble SPs, 15 of  
them can translocate nitrilas protein to cytoplasmic  
compartment. four SPs could guide nitrilase to extracellular  
space while 11 of them could not translocate nitrilas into  
growth medium. Therefore, it seems only these four signal  
It is also suggested that the higher net positive charge  
could be an advantage for increasing the rate of  
translocation desired protein from the phospholipid  
membrane (48). According to Table 3, the net positive  
charge of all evaluated SPs were between 1 and 6 based on  
ProtParam results and they were suitable for the next step  
analysis. Protein instability was indicated by Instability  
index above 40. It means proteins with instability index  
sequences  
(GUB_BACSU,  
SACB_BACAM,  
AMY_BACAM, and SUBF_BACSU) can be introduced as  
applicable SPs. The secretion of heterologous proteins into  
the extracellular space can considerably reduce the  
purification process since cell disruption and the  
subsequent purification would be skipped. Moreovere,  
intracellular expression of recombinannat protein can  
lessen the toxic impacte of target proteins on the production  
of host microorganism and As a result, intracellular  
expression strategies can significantly reduce the cost of  
recombinanat protein production (50).  
As far as we know, this is the first study with the aim of  
investigating the suitable SPs connected with nitrilase by  
evaluating their potential impact on the secretion pathway  
of this protein. This study evaluated 30 different signal  
peptides to introduce the most reliable ones for secreting  
the recombinant nitrilase protein out of Bacillus subtilis  
host. The results of this study showed that GUB_BACSU,  
SACB_BACAM, AMY_BACAM, and SUBF_BACSU  
could be considered as appropriate candidates for the  
nitrilase secretion. However, additional experimental  
studies should be carried out to confirm these results.  
lower than 40 are stable (49). Some of SPs are unstable  
alone but after fusing to nitrilase they would be stable.  
These SPs were chosen for solubility predictions. In silico  
methods for evaluation of the Protein solubility in the  
experimental studies is a very crucial parameter because it  
can cause the formation of inclusion bodies. By  
implementing the SOLpro server, all 23 stable fusion  
proteins were soluble. Hence, according to the stability and  
solubility analysis in Table 3, all signal peptides connected  
to nitrilase were predicted to be stable and none of them  
could be omitted based on these analysis.  
Secretory proteins can be directed to the subcellular  
locations by fusing suitable signal peptides to their N-  
terminus. To more efficient purification and production of  
the heterologous proteins, the ProtCompB server was  
implemented to predict the ultimate destination and  
Table 4: Evaluation of secretion pathways and sub-cellular location of SPs  
Cytoplasmic Cytoplasmic-Membrane Cell wall Extracellular Final prediction site  
0.00 8.80 0.22  
0.00 0.09  
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
0.98  
9.73  
0.01  
2.50  
0.73  
3.33  
9.72  
9.73  
9.72  
0.73  
0.00  
2.92  
2.50  
0.01  
0.01  
0.73  
2.50  
0.01  
2.50  
0.98  
0.01  
3.33  
2.92  
Cytoplasmic-Membrane  
Extracellular  
0.18  
0.12  
2.50  
0.62  
3.33  
0.18  
0.18  
0.18  
0.62  
0.00  
2.48  
2.50  
0.12  
0.12  
0.62  
2.50  
0.12  
2.50  
0.22  
0.06  
3.33  
2.48  
0.32  
02.50  
7.50  
0.00  
0.01  
0.00  
0.01  
7.50  
0.00  
0.00  
2.50  
0.00  
0.32  
7.50  
2.50  
0.32  
2.50  
0.00  
1.78  
0.00  
0.00  
9.55  
2.50  
1.15  
3.33  
0.09  
0.09  
0.09  
1.15  
10.00  
4.60  
2.50  
9.87  
9.55  
1.15  
2.50  
9.55  
2.50  
8.80  
8.16  
3.33  
4.60  
Cytoplasmic-Membrane  
Unknown  
Cytoplasmic  
GUNB_PAELA  
Q93MG8_THIFE  
IRO_THIFE  
Unknown  
Extracellular  
Extracellular  
Extracellular  
0
1
2
3
4
5
6
7
8
9
0
1
2
3
Cytoplasmic  
Cytoplasmic-Membrane  
Unknown  
Unknown  
Cytoplasmic-Membrane  
Cytoplasmic-Membrane  
Cytoplasmic  
RUS2_THIFE  
Unknown  
CY552_THIFE  
THI1_PANTH  
AMYB_PAEPO  
XYND_PAEPO  
CDGT2_PAEMA  
CDGT1_PAEMA  
Cytoplasmic-Membrane  
Unknown  
Cytoplasmic-Membrane  
Cytoplasmic-Membrane  
Unknown  
Unknown  
5
11  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
synthesis. Molecular Biology Research Communications.  
Reference  
2
019;8(1):17-26.  
1
. Kabata-Pendias A, Pendias H. Trace elements in soil and  
plants. 1984.  
2
2
1.Kaur J, Kumar A, Kaur J. Strategies for optimization of  
heterologous protein expression in E. coli: Roadblocks and  
2
. Gijzen HJ, Bernal E, Ferrer H. Cyanide toxicity and cyanide  
degradation in anaerobic wastewater treatment. Water  
Research. 2000;34(9):2447-54.  
reinforcements.  
International  
Journal  
of  
Biological  
Macromolecules. 2018;106:803-22.  
2.Low KO, Mahadi NM, Illias RM. Optimisation of signal  
peptide for recombinant protein secretion in bacterial hosts.  
Applied microbiology and biotechnology. 2013;97(9):3811-26.  
3.Schumann W. Production of recombinant proteins in Bacillus  
subtilis. Advances in applied microbiology. 2007;62:137-89.  
4.Arora D, Khanna N. Method for increasing the yield of properly  
folded recombinant human gamma interferon from inclusion  
bodies. Journal of biotechnology. 1996;52(2):127-33.  
3
4
. Wild SR, Rudd T, Neller A. Fate and effects of cyanide during  
wastewater treatment processes. Science of the total  
environment. 1994;156(2):93-107.  
. Sharma M, Akhter Y, Chatterjee S. A review on remediation of  
cyanide containing industrial wastes using biological systems  
with special reference to enzymatic degradation. World Journal  
of Microbiology and Biotechnology. 2019;35(5):70.  
2
2
5
. Cooper CE, Brown GC. The inhibition of mitochondrial  
cytochrome oxidase by the gases carbon monoxide, nitric oxide,  
hydrogen cyanide and hydrogen sulfide: chemical mechanism  
and physiological significance. Journal of bioenergetics and  
biomembranes. 2008;40(5):533.  
2
2
5.Baneyx F, Mujacic M. Recombinant protein folding and  
misfolding in Escherichia coli. Nature biotechnology.  
2
004;22(11):1399.  
6.Savardashtaki A, Sharifi Z, Hamzehlou S, Farajollahi MM.  
Analysis of immumoreactivity of heterologously expressed  
non-structural protein 4B (NS4B) from hepatitis C virus (HCV)  
genotype 1a. Iranian journal of biotechnology. 2015;13(4):32.  
7.Tjalsma H, Antelmann H, Jongbloed JD, Braun PG, Darmon E,  
Dorenbos R, et al. Proteomics of protein secretion by Bacillus  
subtilis: separating the “secrets” of the secretome. Microbiol  
Mol Biol Rev. 2004;68(2):207-33.  
6
7
8
9
. Geller RJ, Barthold C, Saiers JA, Hall AH. Pediatric cyanide  
poisoning: causes, manifestations, management, and unmet  
needs. Pediatrics. 2006;118(5):2146-58.  
2
2
. Isom GE, Burrows GE, Way JL. Effect of oxygen on the  
antagonism of cyanide intoxication-cytochrome oxidase, in  
vivo. Toxicology and applied pharmacology. 1982;65(2):250-6.  
. Pham JC, Huang DT, McGeorge FT, Rivers EP. Clarification of  
cyanide’s effect on oxygen transport characteristics in a canine  
model. Emergency Medicine Journal. 2007;24(3):152-6.  
. Tshala-Katumbay DD, Ngombe NN, Okitundu D, David L,  
Westaway SK, Boivin MJ, et al. Cyanide and the human brain:  
perspectives from a model of food (cassava) poisoning. Annals  
of the New York Academy of Sciences. 2016;1378(1):50.  
0.Akcil A. Destruction of cyanide in gold mill effluents:  
biological versus chemical treatments. Biotechnology  
Advances. 2003;21(6):501-11.  
1.Mekuto L, Ntwampe SK, Akcil A. An integrated biological  
approach for treatment of cyanidation wastewater. Science of  
the Total Environment. 2016;571:711-20.  
2.Dash RR, Gaur A, Balomajumder C. Cyanide in industrial  
wastewaters and its removal: a review on biotreatment. Journal  
of hazardous materials. 2009;163(1):1-11.  
8.Westers L, Westers H, Quax WJ. Bacillus subtilis as cell  
factory for pharmaceutical proteins:  
approach to optimize the host organism. Biochimica et  
Biophysica Acta (BBA)-Molecular Cell Research.  
004;1694(1-3):299-310.  
a
biotechnological  
2
2
3
3
9.Schallmey M, Singh A, Ward OP. Developments in the use of  
Bacillus species for industrial production. Canadian journal of  
microbiology. 2004;50(1):1-17.  
1
1
1
1
1
0.Simonen M, Palva I. Protein secretion in Bacillus species.  
Microbiology  
and  
Molecular  
Biology  
Reviews.  
1
993;57(1):109-37.  
1.Song Y, Nikoloff JM, Zhang D. Improving protein production  
on the level of regulation of both expression and secretion  
pathways in Bacillus subtilis.  
015;25(7):963-77.  
J Microbiol Biotechnol.  
2
3
3
3
3
3
3
2.Kane JF, Hartley DL. Formation of recombinant protein  
inclusion bodies in Escherichia coli. Trends in Biotechnology.  
3.Gupta N, Balomajumder C, Agarwal V. Enzymatic mechanism  
and biochemistry for cyanide degradation: a review. Journal of  
Hazardous Materials. 2010;176(1-3):1-13.  
4.Trapp S, Larsen M, Pirandello A, Danquah-Boakye J.  
Feasibility of cyanide elimination using plants. ejmp & ep  
1
988;6(5):95-101.  
3.Emanuelsson O, Brunak S, Von Heijne G, Nielsen H. Locating  
proteins in the cell using TargetP, SignalP and related tools.  
Nature protocols. 2007;2(4):953.  
4.Zimmermann R, Eyrisch S, Ahmad M, Helms V. Protein  
translocation across the ER membrane. Biochimica et  
Biophysica Acta (BBA)-Biomembranes. 2011;1808(3):912-24.  
5.Bendtsen JD, Nielsen H, von Heijne G, Brunak S. Improved  
prediction of signal peptides: SignalP 3.0. Journal of molecular  
biology. 2004;340(4):783-95.  
6.Choo KH, Tan TW, Ranganathan S, editors. A comprehensive  
assessment of N-terminal signal peptides prediction methods.  
Bmc Bioinformatics; 2009: BioMed Central.  
7.Gasteiger E, Hoogland C, Gattiker A, Wilkins MR, Appel RD,  
Bairoch A. Protein identification and analysis tools on the  
ExPASy server. The proteomics protocols handbook: Springer;  
(European Journal of Mineral Processing and Environmental  
Protection). 2003;3(1):128-37.  
1
1
1
1
1
5.Desai J, Ramakrishna C. Microbial degradation of cyanides and  
its commercial applications. Journal of scientific & industrial  
research. 1998;57(8):441-53.  
6.Howden AJ, Preston GM. Nitrilase enzymes and their role in  
plantmicrobe  
009;2(4):441-51.  
interactions.  
Microbial  
biotechnology.  
2
7.Kobayashi M, Goda M, Shimizu S. Nitrilase catalyzes amide  
hydrolysis as well as nitrile hydrolysis. Biochemical and  
Biophysical Research Communications. 1999;2(255):549.  
8.Park JM, Sewell BT, Benedik MJ. Cyanide bioremediation: the  
potential of engineered nitrilases. Applied microbiology and  
biotechnology. 2017;101(8):3029-42.  
9.Savardashtaki A, Sarkari B, Arianfar F, Mostafavi-Pour Z.  
Immunodiagnostic value of Echinococcus granulosus  
recombinant B8/1 subunit of antigen B. Iranian journal of  
immunology. 2017;14(2):111-22.  
2
005. p. 571-607.  
8.Walker JM. The proteomics protocols handbook: Springer;  
005.  
3
3
2
9.Hebditch M, Carballo-Amador MA, Charonis S, Curtis R,  
Warwicker J. ProteinSol: a web tool for predicting protein  
solubility from sequence. Bioinformatics. 2017;33(19):3098-  
2
0.Taheri-Anganeh M, Khatami SH, Jamali Z, Savardashtaki A,  
Ghasemi Y, Mostafavipour Z. In silico analysis of suitable  
1
00.  
4
0.Klee EW, Ellis LB. Evaluating eukaryotic secreted protein  
prediction. BMC bioinformatics. 2005;6(1):256.  
signal peptides for secretion of a recombinant alcohol  
dehydrogenase with a key role in atorvastatin enzymatic  
5
12  
Journal of Environmental Treatment Techniques  
2019, Volume 7, Issue 3, Pages: 506-513  
4
1.Mousavi P, Mostafavi-Pour Z, Morowvat MH, Nezafat N,  
Zamani M, Berenjian A, et al. In silico analysis of several  
signal peptides for the excretory production of reteplase in  
Escherichia coli. Current Proteomics. 2017;14(4):326-35.  
2.Zeng R, Gao S, Xu L, Liu X, Dai F. Prediction of pathogenesis-  
related secreted proteins from Stemphylium lycopersici. BMC  
microbiology. 2018;18(1):191.  
3.Baradaran A, Sieo CC, Foo HL, Illias RM, Yusoff K, Rahim  
RA. Cloning and in silico characterization of two signal  
peptides from Pediococcus pentosaceus and their function for  
the secretion of heterologous protein in Lactococcus lactis.  
Biotechnology letters. 2013;35(2):233-8.  
4
4
4
4
4.Diniz W, Canduri F. Bioinformatics: an overview and its  
applications. Genet Mol Res. 2017;16.  
5.Zamani M, Nezafat N, Negahdaripour M, Dabbagh F, Ghasemi  
Y. In silico evaluation of different signal peptides for the  
secretory production of human growth hormone in E. coli.  
International Journal of Peptide Research and Therapeutics.  
2
015;21(3):261-8.  
4
4
6.Nielsen H. Predicting secretory proteins with SignalP. Protein  
function prediction: Springer; 2017. p. 59-73.  
7.Chen H, Kim J, Kendall DA. Competition between functional  
signal peptides demonstrates variation in affinity for the  
secretion pathway. Journal of bacteriology. 1996;178(23):6658-  
6
4.  
4
4
8.Owji H, Nezafat N, Negahdaripour M, Hajiebrahimi A,  
Ghasemi Y. A comprehensive review of signal peptides:  
Structure, roles, and applications. European journal of cell  
biology. 2018;97(6):422-41.  
9.Guruprasad K, Reddy BB, Pandit MW. Correlation between  
stability of a protein and its dipeptide composition: a novel  
approach for predicting in vivo stability of a protein from its  
primary sequence. Protein Engineering, Design and Selection.  
1
990;4(2):155-61.  
5
0.Freudl R. Signal peptides for recombinant protein secretion in  
bacterial expression systems. Microbial cell factories.  
2
018;17(1):52.  
5
13