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Biochemical analysis unveils the mechanism of the interaction between Hsp70s and lipids
Author(s) -
McCallister Chelsea,
Nikolaidis Nikolas
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1021.7
Subject(s) - allosteric regulation , plasma protein binding , lipid bilayer , biochemistry , chaperone (clinical) , hsp70 , cytosol , microbiology and biotechnology , binding site , cyclic nucleotide binding domain , chemistry , membrane lipids , biophysics , cell membrane , biology , membrane , heat shock protein , nucleotide , receptor , enzyme , medicine , pathology , gene
Hsp70s are molecular chaperones essential for cellular homeostasis and survival. Several Hsp70s associate with cellular membranes, where they bind to specific lipids. The association of Hsp70s with lipids anchors them to the plasma membrane, where they regulate cell signaling, stabilizes the lysosomal membrane, and is required for microautophagy. Despite these essential functions the Hsp70‐ lipid interactions remain largely uncharacterized. To understand the molecular mechanism of these interactions we characterized the binding of HSPA1A, a cytosolic hsp70, to lipids. We determined the binding affinities of recombinant HSPA1A to several negatively charged phospholipids and established that although lipid‐binding is mediated largely by the nucleotide‐binding domain, allosteric communication between the two protein domains is crucial for lipid‐binding. We also determined that a conformational change caused by nucleotide‐binding reduces lipid‐binding, while binding of protein substrates has no effect on the lipid‐binding. Next, we determined that the HSPA1A‐lipid interaction is not purely electrostatic and the protein is most probably embedded in the lipid‐bilayer. Finally, we observed that binding of HSPA1A to lipids alters the refolding activity of the chaperone, which suggests that lipid‐binding could represent a new regulatory mechanism of chaperone function. This project was supported by funds from CSUPERB and CSUF to NN