Computational Prediction and Experimental Validation of the Lipid-Binding Regions of Hsp70 Proteins

Hsp70s function in protein folding and refolding, transportation across biological membranes, and are necessary for cellular homeostasis under both physiological and pathological conditions. Apart from their intracellular functions, Hsp70s have also been found in close proximity or bound to biological membranes and in the extracellular milieu. It has been hypothesized that interaction of Hsp70s with specific lipids allows them to translocate and anchor to membranes, and subsequently be secreted. However, these hypotheses have not been directly tested, since the lipid‐binding regions (LBRs) of Hsp70s and the amino acids that mediate these interactions remain uncharacterized. To identify the LBRs of the Hsp70s, we have developed a new algorithm, because the existing protein‐domain‐identification algorithms fail to predict any known lipid‐binding domains in them. Application of our algorithm on HspA1A predicted two regions as putative LBRs. We tested these predictions experimentally and determined that both regions bind to lipids with high affinity. Therefore the experimental results support the predictions of our computational strategy and define two regions that mediate lipid‐binding on the HspA1A. We plan to expand the use of our algorithm to test the evolutionary conservation or divergence of the lipid‐binding function of Hsp70s using Hsp70s from evolutionarily key species. This project was supported by funds from CSUPERB and CSUF to NN