Mapping the Impact in the Substrate Binding Domain of DnaK upon Binding of the Nucleotide Binding Domain of DnaK to the Nucleotide Exchange Factor, GrpE

Presenter

Akshitha Maqtedar

Campus

UMass Amherst

Sponsor

Lila M. Gierasch, Department of Biochemistry and Molecular Biology, UMass Amherst

Schedule

Session 4, 2:30 PM - 3:15 PM [Schedule by Time][Poster Grid for Time/Location]

Location

Poster Board A63, Campus Center Auditorium, Row 4 (A61-A80) [Poster Location Map]

Abstract

     The 70 kDa heat shock proteins (Hsp70s) assist in protein folding through allosteric communication between their nucleotide-binding domain (NBD) and substrate-binding domain (SBD), which are mediated by an interdomain linker. The Hsp70 allosteric cycle is nucleotide-dependent and is modulated by co-chaperones, such as nucleotide exchange factors (NEFs). GrpE, the NEF in E. coli, allows for the replacement of ADP for ATP in Hsp70’s NBD. Many previous studies have drawn contradicting conclusions about what occurs in the SBD upon GrpE binding to the NBD of DnaK. Therefore, we proposed two distinct models, the allosteric model and the direct competition between the tail and binding site model, to explain the proposed effect for what occurs in the SBD in response to the interaction between GrpE and the NBD of DnaK. The two models were tested using fluorescence anisotropy assays where substrate release upon GrpE binding to DnaK was monitored. Current results from these binding assays demonstrate that the K_D of the substrate with GrpE Δ69 is similar to the K_D with GrpE WT, indicating that the allosteric model is representative of the impact in the SBD upon binding of the NBD of DnaK and GrpE. These findings are critical as they will allow us to better understand the mechanism behind the interdomain allosteric signal in DnaK that is triggered by GrpE binding.

Keywords

Molecular Chaperones, Heat Shock Proteins, Nucleotide Exchange Factors

Research Area

Chemistry and Materials Science

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