Rational engineering of Cel5E from Clostridium thermocellum to improve its thermal stability and catalytic activity.

The celH gene from Clostridium thermocellum encodes a protein containing 900 residues and three components, including Cel5E, Lic26a, and carbohydrate-binding domains. Cel5E is a member of the glycoside hydrolase-5 family and is a bifunctional xylanase/cellulase enzyme. We targeted a semi-hydrophobic pocket near the Cel5E active site and theoretically screened mutated variants for enhanced levels of thermal stability. Cel5E mutations were inserted into celH by overlapping polymerase chain reaction, followed by expression of wild-type and mutant enzymes in Escherichia coli BL21 (DE3) and purification by affinity chromatography. Thermal-stabilizing mutations were subjected to molecular dynamics simulation, and measurement of the in vacuo potential energy, van der Waals forces, electrostatic interactions, and net nonbonded potential energies obtained an overall binding affinity of - 64.964 KJ/mol for wild-type Cel5E and - 176.148, - 200.921, and - 120.038 KJ/mol for the N94F, N94W, and E133F mutants, respectively. Additionally, the N94W, N94F, E133F, and N94A variants exhibited 1.92-, 1.29-, 1.1-, and 1.15-fold better carboxymethyl cellulase (CMCase) and 1.46-, 1.29-, 1.11-, and 1.12-fold better ß-glucanase activity on barley ß-glucan relative to the wild-type enzyme. Interestingly, the optimal temperature for CMCase activity by the N94W variant was shifted 2 °C higher than that for the wild-type enzyme. Mutated variants showed improved CMCase and ß-glucanase activity and shifted toward higher temperature of maximum activity.

Molecular dynamics simulation (MDS) analysis of Vibrio cholerae ToxT virulence factor complexed with docked potential inhibitors.

The ToxT transcription factor mediates the transcription of the two major virulence factors in Vibrio cholerae. It has a DNA binding domain made of α4, α5, α6, α7, α8, α9 and α10 helices that is responsible for the transcription of virulence genes. Therefore, it is of interest to screen ToxT against the ZINC ligand database containing data for a million compounds. The QSAR model identified 40 top hits for ToxT. Two target protein complexes with ligands Lig N1 and Lig N2 with high score were selected for molecular dynamics simulation. Simulation data shows that ligands are stable in the DNA binding domain of ToxT. Moreover, Lig N1 and Lig N2 passed pharmacological as well as ADME filters along with g-mmpbsa analysis with binding affinity of -199.831 kJ/mol for Lig N1 and - 286.951 kJ/mol for Lig N2. Moreover, no Lipinski and PhysChem violations were identified. It is further observed that these compounds were not inhibitors of P-glycoprotein, CYP450 and renal organic cation transporters. The LD50 of 2.5804 mol/kg for Lig N1 and 2.7788 mol/kg for Lig N2 was noted with acceptable toxicity index.

Molecular Engineering of the Geobacillus stearothermophilus α-Amylase and Cel5E from Chlostridium thermocellim; In Silico Approach.

BACKGROUND: Considering natural thermal stability, Geobacillus stearothermophilus amylase and Cel5E from Clostridium thermocellum are good candidates for industrial applications. To be compatible with the industrial applications, this enzyme should be stable in the high temperatures, so any improvement in their thermal stability is valuable. OBJECTIVES: Using in silico approach and identifying point mutations in the structure amylase of G. stearothermophilus and Cel5E from C. termocellum we tried to increase thermal stability of the enzymes along with their catalytic activity to reach a new industrial amylase with higher thermostability and an improved function. MATERIALS AND METHODS: In this study we predicted the 3D structure of the enzymes, then simulated the molecular docking study using MolDock, PLANTS, and Lamarkian genetic algorithm as scoring functions for the docking and in silico engineering of the protein aiming to increase the thermal stability and catalytic activity. RESULTS: A series of thermal stability increasing point mutations were exerted around the active site of the enzyme, then by docking procedure, the binding affinity was measured and finally a list of mutations which theoretically improved the increased thermal stability as well as catalytic activity were proposed. CONCLUSIONS: Based on the in silico results obtained the modified enzymes seems to be suitable candidates for considering in both laboratory and industrial scales.

Phylogenetic analysis of otospiralin protein.

BACKGROUND: Fibrocyte-specific protein, otospiralin, is a small protein, widely expressed in the central nervous system as neuronal cell bodies and glia. The increased expression of otospiralin in reactive astrocytes implicates its role in signaling pathways and reparative mechanisms subsequent to injury. Indeed, otospiralin is considered to be essential for the survival of fibrocytes of the mesenchymal nonsensory regions of the cochlea. It seems that other functions of this protein are not yet completely understood. MATERIALS AND METHODS: Amino acid sequences of otospiralin from 12 vertebrates were derived from National Center for Biotechnology Information database. Phylogenetic analysis and phylogeny estimation were performed using MEGA 5.0.5 program, and neighbor-joining tree was constructed by this software. RESULTS: In this computational study, the phylogenetic tree of otospiralin has been investigated. Therefore, dendrograms of otospiralin were depicted. Alignment performed in MUSCLE method by UPGMB algorithm. Also, entropy plot determined for a better illustration of amino acid variations in this protein. CONCLUSION: In the present study, we used otospiralin sequence of 12 different species and by constructing phylogenetic tree, we suggested out group for some related species.

Characterization of a thermostable endoglucanase produced by Isoptericola variabilis sp. IDAH9.

This study aimed to isolate and evaluate the cellulase activity of cellulolytic bacteria in hot springs of Dehloran, Ilam province, Iran. Water and sludge samples were collected from the hot springs and the bacterial enrichment was performed in a medium containing rice barn and carboxymethyl cellulose (CMC). The cultures were incubated at 50 °C in aerobic conditions. The bacteria were isolated on CMC agar (1%) medium. Cellulase assay of the isolates was measured by the evaluation of endoglucanase enzyme activity, which is also called as carboxymethyl cellulase (CMCase). The isolated thermotolerant bacteria were then identified and optimized for the production of CMCase. Moreover, stabilizing elements of the enzyme were identified with in silico approach. The chosen isolate was identified as Isoptericola variabilis sp. IDAH9. The identified strain produced the most thermostable CMCase at a concentration of 5.6 g/L of ammonium sulfate, 9 g/L CMCase or 12 g/L rice bran, 0/6% Tween-80, and 0.2% sucrose. The produced enzyme showed 80% of the residual activity after 1 h of incubation at 65 °C. In silico data indicated that the remaining residual activity was due to the redundant stabilizing elements in the protein structure. Consequently, I. variabilis can be isolated from the extreme environment and has a thermostable endoglucanase which may be used for various applications after studying them.

Characterization of a thermostable endoglucanase produced by Isoptericola variabilis sp. IDAH9

Abstract This study aimed to isolate and evaluate the cellulase activity of cellulolytic bacteria in hot springs of Dehloran, Ilam province, Iran. Water and sludge samples were collected from the hot springs and the bacterial enrichment was performed in a medium containing rice barn and carboxymethyl cellulose (CMC). The cultures were incubated at 50 °C in aerobic conditions. The bacteria were isolated on CMC agar (1%) medium. Cellulase assay of the isolates was measured by the evaluation of endoglucanase enzyme activity, which is also called as carboxymethyl cellulase (CMCase). The isolated thermotolerant bacteria were then identified and optimized for the production of CMCase. Moreover, stabilizing elements of the enzyme were identified with in silico approach. The chosen isolate was identified as Isoptericola variabilis sp. IDAH9. The identified strain produced the most thermostable CMCase at a concentration of 5.6 g/L of ammonium sulfate, 9 g/L CMCase or 12 g/L rice bran, 0/6% Tween-80, and 0.2% sucrose. The produced enzyme showed 80% of the residual activity after 1 h of incubation at 65 °C. In silico data indicated that the remaining residual activity was due to the redundant stabilizing elements in the protein structure. Consequently, I. variabilis can be isolated from the extreme environment and has a thermostable endoglucanase which may be used for various applications after studying them.

A novel mutation pattern of kidney anion exchanger 1 gene in patients with distal renal tubular acidosis in Iran.

INTRODUCTION: Mutations of the anion exchanger 1 (AE1) gene encoding the kidney anion exchanger 1 can result in autosomal dominant or autosomal recessive form of distal renal tubular acidosis (DRTA). This study aimed to report deletion mutations of the AE1 and its impact on Iranian children with DRTA. MATERIALS AND METHODS: Twelve children with DRTA referred to Ali Asghar Children Hospital were investigated for all AE1 gene exons through polymerase chain reaction amplification, DNA sequencing, and bioinformatics analysis. RESULTS: Eleven of 12 patients (91.7%) showed an alteration in AE1 gene with a real hot spot in its exons 11 or 15. Homozygote and heterozygote deletions were confirmed in exon 15 in 5 (41.7%) and 3 (25.0%), respectively. Two patients (16.7%) showed homozygote deletions in exon 11 of AE1 gene, and 1 patient (8.3%) showed point mutation in exon 11. The 3-dimensional structures of the native and these mutant kidney AE1 proteins were determined by the multitemplate method using the Phyre and Hidden Markov Model algorithms. CONCLUSIONS: Parents' consanguinity of these patients reveals that cousins are at a high risk for DRTA. This study is considered as a pilot study showing the importance of AE1 mutations in Iranian children with DRTA and further studies is recommended in this geographic region of the world. These models suggest that alteration in the structures leads to alteration in function and change in the current role of AE1.

Study of the effect of F17A mutation on characteristics of Bacillus thermocatenulatus lipase expressed in Pichia pastoris using in silico and experimental methods.

Bacillus thermocatenulatus lipase 2 (BTL2), a thermoalkalophilic lipase, is the best studied enzyme for its particular properties, which make it useful in different industries. Displacement of conserved phenylalanine 17 (Phe-17) residue in the active site of BTL2 has a critical role in oxyanion hole formation, which is important for enzyme activity. In this study, to facilitate oxyanion hole formation, Phe-17 was substituted with Alanine residue (F17A). The best structures of the opened form of the native and mutated lipases were garnered based on the crystal structures of 2W22. To evaluate catalytic activity, both lipases were docked to a set of ligands using Hex 6.3 software. Following in silico study, both native and mutant btl2 genes were cloned and expressed in Pichia pastoris. Based on the results obtained, the mutation increased lipase lipolytic activity against most of the applied substrates, especially for tributyrin and tricaprylin, by 1.9 and 2.15 fold, respectively. However, optimum temperature and pH were the same for both lipases (60 °C and pH 8.0). As previously reported, it is believed that F17A mutation simplifies oxyanion hole formation and declines steric hindrance in the enzyme active site, which might ultimately lead to more efficient accessibility of substrates.

Virtual screening and pharmacophore design for a novel theoretical inhibitor of macrophage stimulating factor as a metastatic agent.

INTRODUCTION: Metastasis is a crucial aspect of cancer. Macrophage stimulating protein (MSP) is a single chain protein and can be cleaved by serum proteases. MSP has several roles in metastasis. In this in silico study, MSP as a metastatic agent was considered as a drug target. METHODS: Crystallographic structure of MSP was retrieved from protein data bank. To find a chemical inhibitor of MSP, a library of KEGG compounds was screened and 1000 shape complemented ligands were retrieved with FindSite algorithm. Molegro Virtual Docker (MVD) software was used for docking simulation of shape complemented ligands against MSP. Moldock score was used as scoring function for virtual screening and potential inhibitors with more negative binding energy were obtained. PLANS scoring function was used for revaluation of virtual screening data. RESULTS: The top found chemical had binding affinity of -183.55 based on MolDock score and equal to -66.733 PLANTs score to MSP structure. CONCLUSION: Based on pharmacophore model of potential inhibitor, this study suggests that the chemical which was found in this research and its derivate can be used for subsequent laboratory studies.

In silico and experimental characterization of chimeric Bacillus thermocatenulatus lipase with the complete conserved pentapeptide of Candida rugosa lipase.

Lipases are one of the highest value commercial enzymes as they have broad applications in detergent, food, pharmaceutical, and dairy industries. To provide chimeric Bacillus thermocatenulatus lipase (BTL2), the completely conserved pentapeptide (¹¹²Ala-His-Ser-Gln-Gly¹¹6) was replaced with similar sequences (²°7Gly-Glu-Ser-Ala-Gly²¹¹) of Candida rugosa lipase (CLR) at the nucleophilic elbow region. For this purpose, three mutations including A112G, H113E, and Q115A were inserted in the conserved pentapeptide sequence of btl2 gene. Based on the crystal structures of 2W22, the best structure of opened form of the chimeric lipases were garnered using the MODELLER v9.10 software. The native and chimeric lipases were docked to a set of ligands, and a trial version of Molegro Virtual Docker (MVD) software was used to obtain the energy values. Docking results confirmed chimeric lipase to be better than the native lipase. Following the in silico study, cloning experiments were conducted and expression of native and chimeric btl2 gene in Pichia pastoris was performed. The native and chimeric lipases were purified, and the effect of these mutations on characteristics of chimeric lipase studied and then compared with those of native lipase. Chimeric lipase exhibited 1.6-fold higher activity than the native lipase at 55 °C. The highest percentage of both lipases activity was observed at 60 °C and pH of 8.0. The ion Ca²âº slightly inhibited the activity of both lipases, whereas the organic solvent enhanced the lipase stability of chimeric lipase as compared with the native lipase. According to the results, the presence of two glycine residues at the conserved pentapeptide region of this chimeric lipase (¹¹²Gly-Glu-Ser-Ala-Gly¹¹6) may increase the flexibility of the nucleophilic elbow region and affect the enzyme activity level.

In silico modeling of the type 2 IDI enzymes of Bacillus licheniformis, Pseudomonas stutzeri, Streptococcus pyogenes, and Staphylococcus aureus for virtual screening of potential inhibitors of this therapeutic target.

Isopentenyl diphosphate isomerase is an essential enzyme in those living organisms such as pathogenic strains of Streptococcus and Staphylococcus genera which rely on the Mevalonate pathway for the production of isoprenoids. The pathogens contain type 2 IDI in contrast to human that contains type 1 IDI. Therefore, the type 2 IDI may be a potential target for the therapy of some infectious diseases. In the current study, a virtual screening by docking was performed among 2000 chemicals from CoCoCo library to find a specific inhibitor for type 2 IDIs. To this end, the structures of the type 2 IDIs of Bacillus licheniformis, Pseudomonas stutzeri, Streptococcus pyogenes, and Staphylococcus aureus were molded using comparative modeling and Hidden Markov Model (HMM) based prediction. The predicted models were evaluated based on Q-mean and Prosa score. Molegro Virtual Docker with MolDock scoring function was used for measuring the binding affinity of the found inhibitor to the active site of the models. Also the inhibition effect of the compound was virtually tested on the crystallography-solved structures of the Sulfolobus shibatae and Thermus thermophilus type 2 IDIs as well as the Escherichia coli type 1 IDI. Finally, the inhibition effect of the found inhibitor was virtually tested on the human type 1 IDI. Interestingly, the results suggest that the inhibitor efficiently binds to and inhibits the bacterial IDIs especially the type 2 IDIs of pathogens while it is not inhibiting the human IDI.

Virtual screening of m3 protein antagonists for finding a model to study the gammaherpesvirus damaged immune system and chemokine related diseases.

INTRODUCTION: M3 protein is a chemokine decoy receptor involved in pathogenesis of persistent infection with gammaherpesvirus and complications related to the latency of this pathogen. We proposed that antagonists of the M3 would provide a unique opportunity for studying new therapeutic strategies in disordered immune system, immune-deficient states and role of chemokines in pathogenesis development. METHODS: Comparative modeling and fold recognition algorithms have been used for prediction of M3 protein 3-D model. Evaluation of the models using Q-mean and ProSA-web score, has led to choosing predicted model by fold recognition algorithm as the best model which was minimized regarding energy level using Molegro Virtual Docker 2011.4.3.0 (MVD) software. Pockets and active sites of model were recognized using MVD cavity detection, and MetaPocket algorithms. Ten thousand compounds accessible on KEGG database were screened; MVD was used for computer simulated docking study; MolDock SE was selected as docking scoring function and final results were evaluated based on MolDock and Re-rank score. RESULTS: Docking data suggested that prilocaine, which is generally applied as a topical anesthetic, binds strongly to 3-D model of M3 protein. CONCLUSION: This study proposes that prilocaine is a potential inhibitor of M3 protein and possibly has immune enhancing properties.

Comparative modeling of CCRL1, a key protein in masked immune diseases and virtual screening for finding inhibitor of this protein.

Human CCRL1 belongs to the family of silent chemokine receptors. This transmembrane protein plays a role in blunting function of chemokines through binding to them. This will attenuate immune responses. Interaction between CCRL1 and CCL21 determines this immune extinction. Thus inhibiting the action of this atypical chemokine seems to stimulate immune responses especially in the case of suppressed and immune deficient conditions. In this study we predicted 3D structure of CCRL1 using comparative modeling and Hiddebn Markov Model algorithm. Final predicted model optimized by Modeller v9.8 and minimized regarding energy level using UCSF chimera candidate version1.5.3. ClasPro webserver was used to find interacting residues between CCRL1 and CCL21. Interacting residues were used as target for chemical inhibitors by simulated docking study. For finding potential inhibitors, library of KEGG compounds screened and 97 obtained chemicals docked against interacting residues between CCRL1- CCL21 and MolDock was used as docking scoring function. Results indicated that Hexadecanal is a potential inhibitor of CCRL1- CCL21 interaction. Inhibition of this interaction will increase intercellular level of CCl21 and interaction between CCL21 and CCR7 causes immune potentiaiton.

Comparative modeling of DszC, an enzyme in biodesulfurization, and performing in silico point mutation for increasing tendency to oil.

Desulfurization protein named DszC from Rhodococcus erythropolis is the key enzyme for biodesulforization of dibenzothiophene (DBT) in 4S pathway, which is a pathway with four enzymes. DszC enzyme biodesulfurizes DBT and its derivatives in oil components and biphasic systems. It functions well at the oil- water interface. In this study point mutation performed in DszC enzyme regarding to increase protein hydrophobicity and stability for application in immobilized form. 3D model of DszC predicted using Phyre2, SAM-T08 and M4t servers. I-Mutant 2 server used to determine potential spots for point mutation, and Molegro Virtual Docker (MVD) used for performing point mutation on 3D model. Hydrophobicity plots generated by Bioedit version 7.0.8.0 in Kyte-Doolittle scale indicated that protein hydrophobicity is increased after mutation. Also protein stability increased 26.11 units in scale of DDC2.