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      MoMA-LigPath: a web server to simulate protein–ligand unbinding

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          Abstract

          Protein–ligand interactions taking place far away from the active site, during ligand binding or release, may determine molecular specificity and activity. However, obtaining information about these interactions with experimental or computational methods remains difficult. The computational tool presented in this article, MoMA-LigPath, is based on a mechanistic representation of the molecular system, considering partial flexibility, and on the application of a robotics-inspired algorithm to explore the conformational space. Such a purely geometric approach, together with the efficiency of the exploration algorithm, enables the simulation of ligand unbinding within short computing time. Ligand unbinding pathways generated by MoMA-LigPath are a first approximation that can provide useful information about protein–ligand interactions. When needed, this approximation can be subsequently refined and analyzed using state-of-the-art energy models and molecular modeling methods. MoMA-LigPath is available at http://moma.laas.fr. The web server is free and open to all users, with no login requirement.

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          How do substrates enter and products exit the buried active site of cytochrome P450cam? 1. Random expulsion molecular dynamics investigation of ligand access channels and mechanisms.

          V. Lounnas, Kristin R. Wade, S Lüdemann (2000)
          Cytochrome P450s form a ubiquitous protein family with functions including the synthesis and degradation of many physiologically important compounds and the degradation of xenobiotics. Cytochrome P450cam from Pseudomonas putida has provided a paradigm for the structural understanding of cytochrome P450s. However, the mechanism by which camphor, the natural substrate of cytochrome P450cam, accesses the buried active site is a long-standing puzzle. While there is recent crystallographic and simulation evidence for opening of a substrate-access channel in cytochrome P450BM-3, for cytochrome P450cam, no such conformational changes have been observed either in different crystal structures or by standard molecular dynamics simulations. Here, a novel simulation method, random expulsion molecular dynamics, is presented, in which substrate-exit channels from the buried active site are found by imposing an artificial randomly oriented force on the substrate, in addition to the standard molecular dynamics force field. The random expulsion molecular dynamics method was tested in simulations of the substrate-bound structure of cytochrome P450BM-3, and then applied to complexes of cytochrome P450cam with different substrates and with product. Three pathways were identified, one of which corresponds to a channel proposed earlier on the basis of crystallographic and site-directed mutagenesis data. Exit via the water-filled channel, which was previously suggested to be a product exit channel, was not observed. The pathways obtained by the random expulsion molecular dynamics method match well with thermal motion pathways obtained by an analysis of crystallographic B-factors. In contrast to large backbone motions (up to 4 A) observed in cytochrome P450BM-3 for the exit of palmitoleic acid, passage of camphor through cytochrome P450cam only requires small backbone motions (less than 2.4 A) in conjunction with side-chain rotations. Concomitantly, in almost all the exit trajectories, salt-links that have been proposed to act as ionic tethers between secondary structure elements of the protein, are perturbed. Copyright 2000 Academic Press.
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            Zinc-ligand interactions modulate assembly and stability of the insulin hexamer -- a review.

            Jeff Dunn (2005)
            Zinc and calcium ions play important roles in the biosynthesis and storage of insulin. Insulin biosynthesis occurs within the beta-cells of the pancreas via preproinsulin and proinsulin precursors. In the golgi apparatus, proinsulin is sequestered within Zn(2+)- and Ca(2+)-rich storage/secretory vesicles and assembled into a Zn(2+) and Ca(2+) containing hexameric species, (Zn(2+))(2)(Ca(2+))(Proin)(6). In the vesicle, (Zn(2+))(2)(Ca(2+))(Proin)(6) is converted to the insulin hexamer, (Zn(2+))(2)(Ca(2+))(In)(6), by excision of the C-peptide through the action of proteolytic enzymes. The conversion of (Zn(2+))(2)(Ca(2+))(Proin)(6)to (Zn(2+))(2)(Ca(2+))(In)(6) significantly lowers the solubility of the hexamer, causing crystallization within the vesicle. The (Zn(2+))(2)(Ca(2+))(In)(6) hexamer is an allosteric protein that undergoes ligand-mediated interconversion among three global conformation states designated T(6), T(3)R(3) and R(6). Two classes of allosteric sites have been identified; hydrophobic pockets (3 in T(3)R(3) and 6 in R(6)) that bind phenolic ligands, and anion sites (1 in T(3)R(3) and 2 in R(6)) that bind monovalent anions. The allosteric states differ widely with respect to the physical and chemical stability of the insulin subunits. Fusion of the vesicle with the plasma membrane results in the expulsion of the insulin crystals into the intercellular fluid. Dissolution of the crystals, dissociation of the hexamers to monomer and transport of monomers to the liver and other tissues then occurs via the blood stream. Insulin action then follows binding to the insulin receptors. The role of Zn(2+) in the assembly, structure, allosteric properties, and dynamic behavior of the insulin hexamer will be discussed in relation to biological function.
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              The PyMOL molecular graphics system

              L. Schrödinger, LLC Schrodinger, L. Schrodinger … (2010)
              Article 0 comments Cited 48 times – based on 0 reviews     Review now
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                Author and article information

                Journal
                Journal ID (nlm-ta): Nucleic Acids Res
                Journal ID (iso-abbrev): Nucleic Acids Res
                Journal ID (publisher-id): nar
                Journal ID (hwp): nar
                Title: Nucleic Acids Research
                Publisher: Oxford University Press
                ISSN (Print): 0305-1048
                ISSN (Electronic): 1362-4962
                Publication date (Print): July 2013
                Publication date (Electronic): 11 May 2013
                Publication date PMC-release: 11 May 2013
                Volume: 41
                Issue: Web Server issue
                Pages: W297-W302
                Affiliations
                1CNRS, LAAS, 7 av du colonel Roche, F-31400 Toulouse, France and 2Univ de Toulouse, LAAS, F-31400 Toulouse, France
                Author notes
                *To whom correspondence should be addressed. Tel: +33 561336345; Fax: +33 561336455; Email: juan.cortes@ 123456laas.fr
                Article
                Publisher ID: gkt380
                DOI: 10.1093/nar/gkt380
                PMC ID: 3692135
                PubMed ID: 23671332
                SO-VID: 5182bd1b-f5fd-4dd0-ad57-e24ff0bb7f77
                Copyright © © The Author(s) 2013. Published by Oxford University Press.
                License:

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/3.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                Date received : 31 January 2013
                Date revision received : 8 April 2013
                Date accepted : 18 April 2013
                Page count
                Pages: 6
                Categories
                Subject: Articles
                Custom metadata
                cover-date 1 July 2013

                ScienceOpen disciplines: Genetics
                Data availability:
                ScienceOpen disciplines: Genetics

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