Effects of the Inter-ring Communication in GroEL Structural and Functional Asymmetry

• Published in: The Journal of biological chemistry 1997-12, Vol.272 (52), p.32925-32932
• Main Authors: Llorca, Oscar, Pérez-Pérez, Julián, Carrascosa, José L., Galán, Asier, Muga, Arturo, Valpuesta, José M.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Adenylyl Imidodiphosphate - metabolism; Animals; Chaperonin 10 - chemistry; Chaperonin 10 - metabolism; Chaperonin 60 - chemistry; Chaperonin 60 - genetics; Chaperonin 60 - ultrastructure; Malate Dehydrogenase - metabolism; Microscopy, Electron; Point Mutation; Potassium - metabolism; Protein Binding; Protein Conformation; Protein Folding; Swine; Thiosulfate Sulfurtransferase - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.52.32925

The chaperonin GroEL consists of a double-ring structure that assists protein folding in the presence of GroES and ATP. Recent studies suggest that the 7-mer ring is the functional unit where protein folding takes place. Nevertheless, both GroEL rings are required to complete the reaction cycle through signals transmitted between the two rings. Electron microscopy, image processing, and biochemical analysis of GroEL, a single-ring mutant (SR1) and a inter-ring communication affected mutant (A126V), in the presence of ATP and adenylyl imidodiphosphate, have allowed the identification of a conformational change in the apical domains that is strictly dependent on the communication between the two GroEL rings. It is deduced from these results that the binding of nucleotide to both GroEL rings generates, as a consequence of the inter-ring communication, a functionally and structurally asymmetric particle. This asymmetric particle has a ring with a small conformational change in its apical domains and high affinity toward unfolded substrate and GroES, and the other ring has a larger conformational change in its apical domains and lower affinity toward substrate and GroES.