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Updated: Jul 17, 2026

Escherichia coli -Based Complementation Assay to Study the Chaperone Function of Heat Shock Protein 70
Published on: March 8, 2024
A water mediated electrostatic interaction gives thermal stability to the "tail" region of the GrpE protein from E.
Andrew F Mehl1, Borries Demeler, Afaq Zraikat
1Department of Chemistry, Knox College, Galesburg, IL 61401, USA. amehl@knox.edu
Abstract:
The GrpE protein from E. coli is a homodimer with an unusual structure of two long paired alpha-helices from each monomer interacting in a parallel arrangement to form a "tail" at the N-terminal end. Using site-directed mutagenesis, we show that there is a key electrostatic interaction involving R57 (mediated by a water molecule) that provides thermal stability to this "tail" region. The R57A mutant showed a drop in T (m) of 8.5 degrees C and a smaller DeltaH (u) (unfolding) compared to wild-type for the first unfolding transition, but no significant decrease in dimer stability as shown through equilibrium analytical ultracentrifugation studies. Another mutant (E94A) at the dimer interface showed a decrease in DeltaH (u )but no drop in T (m) for the second unfolding transition and a slight increase in dimer stability.
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