Structural highlights
FunctionQ548M1_ECOLX Prevents misfolding and promotes the refolding and proper assembly of unfolded polypeptides generated under stress conditions (By similarity).[RuleBase:RU000419][HAMAP-Rule:MF_00600] Publication Abstract from PubMedThe GroE chaperonins assist substrate protein (SP) folding by cycling through several conformational states. With each cycle the SP is, in turn, captured, unfolded, briefly encapsulated (t1/2 approximately 1 s), and released by the chaperonin complex. The protein-folding functional form is the US-football-shaped GroEL:GroES2 complex. We report structures of two such "football" complexes to approximately 3.7-A resolution; one is empty whereas the other contains encapsulated SP in both chambers. Although encapsulated SP is not visible on the electron density map, using calibrated FRET and order-of-addition experiments we show that owing to SP-catalyzed ADP/ATP exchange both chambers of the football complex encapsulate SP efficiently only if the binding of SP precedes that of ATP. The two rings of GroEL thus behave as a parallel processing machine, rather than functioning alternately. Compared with the bullet-shaped GroEL:GroES1 complex, the GroEL:GroES2 football complex differs conformationally at the GroEL-GroES interface and also at the interface between the two GroEL rings. We propose that the electrostatic interactions between the epsilon-NH3+ of K105 of helix D in one ring with the negatively charged carboxyl oxygen of A109 at the carboxyl end of helix D of the other ring provide the structural basis for negative inter-ring cooperativity. Formation and structures of GroEL:GroES2 chaperonin footballs, the protein-folding functional form.,Fei X, Ye X, LaRonde NA, Lorimer GH Proc Natl Acad Sci U S A. 2014 Aug 18. pii: 201412922. PMID:25136110[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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