Molecular Dynamics and Docking Investigations of Several Zoanthamine- Type Marine Alkaloids as Matrix Metaloproteinase-1 Inhibitors

Zoanthamine-type alkaloids display a wide spectrum of biological effects. This study aimed to examine the inhibitory effects of norzoanthamine and its ten homologues of zoanthamine class on human fibroblast collagenase by modeling a three-dimensional structure of the ligands at collagenase using energy minimization, docking, molecular dynamics simulation and MM-PB/GBSA binding free energy calculations. The results showed that zoanthamide, zooxathellamine and enol-iminium form of norzoanthamine, with lower binding free energies than other compounds, are potent inhibitors of collagenase. However, the enol-iminium form of norzoanthamine showed a more inhibitory activity against collagenase than its keto form. This suggests that it can be used for treatment of many diseases such as osteoporosis, autoimmune diseases, and cancer. Zinc-binding residues such as His 118, His 122 and His 128 for hydrogen bonds and Leu 81, Tyr 110, Val 115, Leu 126, Pro 138, Ser 139 for hydrophobic interactions should be considered for designing an inhibitor for collagenase. Our theoretical results and MM/GBSA binding free energy calculations are consistent with experimental studies. Abbreviation MD: Molecular dynamics; RMSD: Root mean square deviation; MM-PB/GBSA: Molecular mechanics Poisson-Boltzmann/General Born surface area, DFT: density functional theory, B3LYP: Becke, three-parameter, Lee-Yang-Parr, RESP: Restrained electrostatic surfacepotentia

In silico designing and creation a new generation of reteplase with more fibrin specificity

Introduction: Reteplase is a fibrin-specific thrombolytic drug and non-glycosylated modified recombinant form of human tissue plasminogen activator (t-PA). It is containing kringle-2 and serine protease domains but the epidermal growth factor and fibronectin finger domains are absent. The lack of finger domain in reteplase cause decrease fibrin specificity. Since the enhancing fibrin specificity is one of the aim for development new thrombolytic drug, due to decreasing side effect such as hemorrhage, also reteplase is non-glycosylated and can be produced in bacterial system at low cost, in this study a new generation of reteplase designed with more fibrin specificity.  Methods and Results: According to the sequence of protein drugswith more fibrin specificity, mutations in reteplase sequence consist of substitution mutation in Kringle 2 domains and adding sequence of mutated finger domain to reteplase sequence. 3D structure of this new reteplase was created by Modeller9.17 software and then simulated by Gromacs 5 software for 20 ns. Docking simulation was performed between new and wild reteplase with fibrin by HADDOCK server separately. The results showed that new reteplase has better interaction with fibrin compared with wild type (table1). Parameter Wild reteplase New  reteplase HADDOCK score* -35.8 +/- 8.3 -43.2 +/- 21.3             *More negative score is better score  Conclusions: In this study a new generation of reteplase with more fibrin specificity was designed in silico. Since the production of reteplase has low cost compared with tPA, improvement its structure to desirable features such as increasing fibrin specificity, can be a way to achieve a favorable thrombolytic drug

Molecular dynamics and docking investigations of several zoanthamine-type marine alkaloids as matrix metaloproteinase-1 inhibitors

Zoanthamine-type alkaloids display a wide spectrum of biological effects. This study aimed to examine the inhibitory effects of norzoanthamine and its ten homologues of zoanthamine class on human fibroblast collagenase by modeling a three-dimensional structure of the ligands at collagenase using energy minimization, docking, molecular dynamics simulation and MM-PB/GBSA binding free energy calculations. The results showed that zoanthamide, zooxathellamine and enol-iminium form of norzoanthamine, with lower binding free energies than other compounds, are potent inhibitors of collagenase. However, the enol-iminium form of norzoanthamine showed a more inhibitory activity against collagenase than its keto form. This suggests that it can be used for treatment of many diseases such as osteoporosis, autoimmune diseases, and cancer. Zinc-binding residues such as His 118, His 122 and His 128 for hydrogen bonds and Leu 81, Tyr 110, Val 115, Leu 126, Pro 138, Ser 139 for hydrophobic interactions should be considered for designing an inhibitor for collagenase. Our theoretical results and MM/GBSA binding free energy calculations are consistent with experimental studies

Designing a new tetrapeptide to inhibit the BIR3 domain of the XIAP protein via molecular dynamics simulations

The XIAP protein is a member of apoptosis proteins family. The XIAP protein plays a central role in the inhibition of apoptosis and consists of three Baculoviral IAP Repeat domains. The BIR3 domain binds directly to the N-terminal of caspase-9 and therefore it inhibits apoptosis. N-terminal tetrapeptide region of SMAC protein can bind to BIR3, inhibit it and subsequently induce apoptosis. In this study, fifteen tetrapeptides were docked into the BIR3 domain and then 10 ns molecular dynamics simulations were performed on each of the BIR3-peptide complex obtained from docking. MM/PBSA method was subsequently used to calculate the binding free energy of peptides to BIR3. The results of MM/PBSA method were in good coordination with docking and existing expermental results.  The results showed the most potent peptides with the lowest binding free energy for binding to BIR3 included ATPF, AKPW and ARPF peptides. Also, investigation of bonds between these peptides and BIR3 domain in the final structure of complexes showed that Leu 307, Thr 308, Glu 314 and Tyr 324 of the BIR3 domain were essential for binding of peptides. Energy decomposition results for binding these peptides to the BIR3 domain during MD simulation was inconsistent with previous results and approved the roles of the same residues. The higher affinity of these peptides relative to native peptide (AVPI) and comparing them with other peptides revealed that the existence of positive charge in the second position and the existence of the aromatic group in the fourth position led to more binding affinity

Theoretical design of a new chimeric protein for the treatment of breast cancer

p28 and NRC peptides are two anticancer peptides with various mechanisms have shown to be effective against breast cancer. Therefore, it seems that construction of a chimeric protein containing the two peptides might cause synergistic cytotoxic effects. However, since the two peptides bear opposite charges, production of a chimeric protein in which the two moieties do not intervene each other is difficult. In this study, our goal was to find a suitable peptide linker for the new chimeric protein in a manner that none of the peptides intervene the other’s function. We selected some linkers with different characteristics and lengths and created a small library of the chimeric proteins harboring these linkers. Homology modeling and molecular dynamic simulation revealed that (PA)5P and (EAAAK)3 linkers can separate the p28 and NRC peptides effectively. Thus, the chimeric protein linked with (PA)5P or (EAAAK)3 linkers might show synergistic and stronger anticancer effects than the separate peptide moieties because they could exert their cytotoxic effects freely which is not influenced by the other part

Evolutionary trajectories of beta-lactamase NDM and DLST cluster in <i>Pseudomonas aeruginosa</i>: finding the putative ancestor

Pseudomonas aeruginosa has different antibiotic resistance pathways, such as broad-spectrum lactamases and metallo-β-lactamases (MBL), penicillin-binding protein (PBP) alteration, and active efflux pumps. Polymerase chain reaction (PCR) and sequencing methods were applied for double-locus sequence typing (DLST) and New Delhi metallo-β-lactamase (NDM) typing. We deduced the evolutionary pathways for DLST and NDM genes of P. aeruginosa using phylogenetic network. Among the analyzed isolates, 62.50% of the P. aeruginosa isolates were phenotypically carbapenem resistance (CARBR) isolates. Characterization of isolates revealed that the prevalence of blaNDM, blaVIM, blaIMP, undetermined carbapenemase, and MexAB-OprM were 27.5%, 2%, 2.5%, 12.5%, and 15%, respectively. The three largest clusters found were DLST t20–105, DLST t32–39, and DLST t32–52. The network phylogenic tree revealed that DLST t26–46 was a hypothetical ancestor for other DLSTs, and NDM-1 was as a hypothetical ancestor for NDMs. The combination of the NDM and DLST phylogenic trees revealed that DLST t32–39 and DLST tN2-N3 with NDM-4 potentially derived from DLST t26–46 along with NDM-1. Similarly, DLST t5–91 with NDM-5 diversified from DLST tN2-N3 with NDM-4. This is the first study in which DLST and NDM evolutionary routes were performed to investigate the origin of P. aeruginosa isolates. Our study showed that the utilization of medical equipment common to two centers, staff members common to two centers, limitations in treatment options, and prescription of unnecessary high levels of meropenem are the main agents that generate new types of resistant bacteria and spread resistance among hospitals.</p

In silico and in vitro effects of the I30T mutation on myelin protein zero instability in the cell membrane

Charcot-Marie-Tooth (CMT) diseases are a heterogeneous group of genetic peripheral neuropathies caused by mutations in a variety of genes, which are involved in the development and maintenance of peripheral nerves. Myelin protein zero (MPZ) is expressed by Schwann cells, and MPZ mutations can lead to primarily demyelinating polyneuropathies including CMT type 1B. Different mutations demonstrate various forms of disease pathomechanisms, which may be beneficial in understanding the disease cellular pathology. Our molecular dynamics simulation study on the possible impacts of I30T mutation on the MPZ protein structure suggested a higher hydrophobicity and thus lower stability in the membranous structures. A study was also conducted to predict native/mutant MPZ interactions. To validate the results of the simulation study, the native and mutant forms of the MPZ protein were separately expressed in a cellular model, and the protein trafficking was chased down in a time course pattern. In vitro studies provided more evidence on the instability of the MPZ protein due to the mutation. In this study, qualitative and quantitative approaches were adopted to confirm the instability of mutant MPZ in cellular membranes