Unraveling Chaperone Selectivity: Investigating the Substrate Binding Characteristics of Mammalian Hsp70s

Presenter: Sydney T. Mager

Faculty Sponsor: Lila M. Gierasch

School: UMass Amherst

Research Area: Biochemistry and Molecular Biology

Session: Poster Session 5, 3:15 PM - 4:00 PM, Concourse, B4

ABSTRACT

Hsp70 molecular chaperones play a wide array of essential roles in the cell by exploiting their ability to bind incompletely folded client proteins. As such, Hsp70s serve a critical role in cell survival protecting against stress. Our past study of the E. coli Hsp70, DnaK, bound to short peptides revealed many details of the interaction between a model substrate and the “pockets” of the canonical binding cleft within the chaperone substrate-binding domain (SBD). A major finding was that peptides bound the SBD cleft in either N- to C- or C- to N- orientations with nearly equal frequencies. The current study asks: What determines preferred orientation in the bound substrate, and are the binding properties of different Hsp70 chaperones distinct? In particular, this project seeks to identify and compare the binding characteristics of two major human cytoplasmic Hsp70s, Hsc70 (constitutively expressed) and HspA1 (stress- induced). While the two human Hsp70s share 82% sequence identity, differences are found in the residues that line the central binding pocket of the SBD. Because of this, we expect there to be differences in substrate binding selectivity, and potentially their responses to drug candidates. Here we use NMR and cross-linking methods developed in our past study with DnaK and compare modes of binding in the human Hsp70s.  Model peptides examined include a “palindromic” peptide, central residue variant peptides, and examples of naturally occurring Hsp70 clients.  We speculate that the binding properties of different Hsp70 molecular chaperones enable them to perform their physiological functions more effectively. 

RELATED ABSTRACTS