Review: A structural view of the GroE chaperone cycle

The GroE chaperone system consists of two ring-shaped oligomeric components whose association creates different functional states. The most remarkable property of the GroE system is the ability to fold proteins under conditio ns where spontaneous folding cannot occur. To achieve this, a fully functio nal system consisting of GroEL, the cochaperone GroES, and ATP is necessary . Driven by ATP binding and hydrolysis, this system cycles through differen t conformational stages, which allow binding, folding, and release of subst rate proteins. Some aspects of the ATP-driven reaction cycle are still unde r debate. One of these open questions is the importance of so-called "footb all" complexes consisting of GroEL and two bound GroES rings. Here, we summ arize the evidence for the functional relevance of these complexes and thei r involvement in the efficient folding of substrate proteins. (C) 2001 Acad emic Press.