title: Functional significance of symmetrical versus asymmetrical GroEL-GroES chaperonin complexes.
abstract: The Escherichia coli chaperonin GroEL and its regulator GroES are thought to mediate adenosine triphosphate-dependent protein folding as an asymmetrical complex, with substrate protein bound within the GroEL cylinder. In contrast, a symmetrical complex formed between one GroEL and two GroES oligomers, with substrate protein binding to the outer surface of GroEL, was recently proposed to be the functional chaperonin unit. Electron microscopic and biochemical analyses have now shown that unphysiologically high magnesium concentrations and increased pH are required to assemble symmetrical complexes, the formation of which precludes the association of unfolded polypeptide. Thus, the functional significance of GroEL:(GroES)2 particles remains to be demonstrated.
authors.affiliation: Maurice E. Müller Institute, Biozentrum, University of Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Engel
authors.forename: M K
authors.initials: MK
authors.lastname: Hayer-Hartl
authors.forename: K N
authors.initials: KN
authors.lastname: Goldie
authors.forename: G
authors.initials: G
authors.lastname: Pfeifer
authors.forename: R
authors.initials: R
authors.lastname: Hegerl
authors.forename: S
authors.initials: S
authors.lastname: Müller
authors.forename: A C
authors.initials: AC
authors.lastname: da Silva
authors.forename: W
authors.initials: W
authors.lastname: Baumeister
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D018835:Chaperonin 10 / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D018834:Chaperonin 60 / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D017348:Microscopy, Electron, Scanning Transmission; D017510:Protein Folding
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium