Xu, Linan and Hasin, Naushaba and Shen, Manli and He, Jianwei and Xue, Youlin and Zhou, Xiaohong and Perrett, Sarah and Song, Youtao and Jones, Gary W. (2013) Using Steered Molecular Dynamics to Predict and Assess Hsp70 Substrate-Binding Domain Mutants that Alter Prion Propagation. PLoS Computational Biology, 9 (1). ISSN 1553-734X

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Abstract

Genetic screens using Saccharomyces cerevisiae have identified an array of cytosolic Hsp70 mutants that are impaired in the ability to propagate the yeast [PSI+] prion. The best characterized of these mutants is the Ssa1 L483W mutant (so-called SSA1-21), which is located in the substrate-binding domain of the protein. However, biochemical analysis of some of these Hsp70 mutants has so far failed to provide major insight into the specific functional changes in Hsp70 that cause prion impairment. In order to gain a better understanding of the mechanism of Hsp70 impairment of prions we have taken an in silico approach and focused on the Escherichia coli Hsp70 ortholog DnaK. Using steered molecular dynamics simulations (SMD) we demonstrate that DnaK variant L484W (analogous to SSA1-21) is predicted to bind substrate more avidly than wild-type DnaK due to an increase in numbers of hydrogen bonds and hydrophobic interactions between chaperone and peptide. Additionally the presence of the larger tryptophan side chain is predicted to cause a conformational change in the peptide-binding domain that physically impairs substrate dissociation. The DnaK L484W variant in combination with some SSA1-21 phenotypic second-site suppressor mutations exhibits chaperone-substrate interactions that are similar to wild-type protein and this provides a rationale for the phenotypic suppression that is observed. Our computational analysis fits well with previous yeast genetics studies regarding the functionality of the Ssa1-21 protein and provides further evidence suggesting that manipulation of the Hsp70 ATPase cycle to favor the ADP/substrate-bound form impairs prion propagation. Furthermore, we demonstrate how SMD can be used as a computational tool for predicting Hsp70 peptide-binding domain mutants that impair prion propagation.

Item Type:	Article
Keywords:	Steered Molecular Dynamics; Hsp70 Substrate-Binding Domain Mutants; Prion Propagation;
Academic Unit:	Faculty of Science and Engineering > Biology
Item ID:	4297
Depositing User:	Dr. Gary Jones
Date Deposited:	09 Apr 2013 13:57
Journal or Publication Title:	PLoS Computational Biology
Publisher:	Public Library of Science
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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