The PDB and protein homeostasis: from chaperones to degradation and disaggregase machines

This review contains a personal account of the role played by the PDB in the development of the field of molecular chaperones and protein homeostasis, from the viewpoint of someone who experienced the concurrent advances in the structural biology, electron microscopy, and chaperone fields. The emphasis is on some key structures, including those of Hsp70, GroEL, Hsp90, and small heat shock proteins, that were determined as the molecular chaperone concept and systems for protein quality control were emerging. These structures were pivotal in demonstrating how seemingly nonspecific chaperones could assist the specific folding pathways of a variety of substrates. Moreover, they have provided mechanistic insights into the ATPase machinery of complexes such as GroEL/GroES that promote unfolding and folding and the disaggregases that extract polypeptides from large aggregates and disassemble amyloid fibers. The PDB has provided a framework for the current success in curating, evaluating, and distributing structural biology data, through both the PDB and the EMDB.