Entering deeper into the mysteries of the GroEL–GroES nanomachine

In the densely populated intracellular milieu, polypeptides are at constant risk of nonspecific interactions and aggregation, posing a threat to essential cellular functions. Cells rely on a network of protein folding factors to deal with this challenge. The Hsp60 family of molecular chaperones, which depend on ATP for function, stands out in the proteostasis network by a characteristic structure comprising two multimeric rings arranged back to back. This review provides an updated overview of GroEL, the bacterial Hsp60, and its GroES (Hsp10) cofactor. Specifically, we highlight recent breakthroughs in understanding the intricate folding mechanisms of the GroEL–GroES nanomachine and explore the newly discovered interaction between GroEL and the chaperedoxin CnoX. Despite considerable research on the GroEL–GroES system, numerous questions remain to be explored.