Towards enhanced understanding of protein folding in the cell (219.1)

Abstract

Major challenges arise when we attempt to apply lessons from study of protein folding in vitro to folding of a protein in vivo where conditions are very different from high‐dilution test tube experiments. Strikingly, proteins generally fold successfully in vivo, even at concentrations higher than the threshold for aggregation, because the protein homeostasis network, including chaperones and degradation machinery, facilitates folding under cellular conditions. This talk will describe two aspects of the function of the protein homeostasis network: 1) Using primarily NMR, we have studied the allosteric mechanism of the Hsp70 chaperone family and found that nucleotide‐dependent substrate affinity is a consequence of ligand‐modulation of domain conformational ensembles. 2) We are exploring how the E. coli protein homeostasis network modulates protein folding. Predictions from our computational model, FoldEco (Powers et al., Cell Reports 1, 265 [2012]), are being tested experimentally. Up‐regulation of the protein homeostasis network benefited several test proteins, as did enhanced expression of the Lon degradation enzyme. Over‐expression of individual chaperones had substrate‐dependent effects. These results suggest that the cell handles the folding load of the proteome by concerted action of the proteostasis network.Supported by NIH grants GM027616 and GM101644.