Alteration of the quaternary structure of cpn60 modulates chaperonin-assisted folding. Implications for the mechanism of chaperonin action

• Published in: The Journal of biological chemistry 1994-01, Vol.269 (4), p.2447-2451
• Main Authors: MENDOZA, J. A, DEMELER, B, HOROWITZ, P. M
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Binding and carrier proteins; Biological and medical sciences; Cattle; Chaperonin 60; Circular Dichroism; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Heat-Shock Proteins - chemistry; Heat-Shock Proteins - metabolism; Kinetics; Liver - enzymology; Models, Structural; Protein Conformation; Protein Folding; Proteins; Thiosulfate Sulfurtransferase - chemistry; Thiosulfate Sulfurtransferase - metabolism; Trypsin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)41966-1

Chaperonin-mediated, in vitro folding of rhodanese by the intact protein cpn60 has previously been shown to require cpn10 and ATP hydrolysis (Martin, J., Langer, T., Boteva, R., Schramel, A., Horwich, A. L., and Hartl, F.-U. (1991) Nature 352, 36-42; Mendoza, J. A., Rogers, E., Lorimer, G. H., and Horowitz, P. M. (1991) J. Biol. Chem. 266, 13044-13049). The present work demonstrates that the rhodanese-cpn60 complex can be dissociated by urea to allow folding to proceed, thus removing the obligatory requirement for cpn10 and ATP. Analytical ultracentrifugation and circular dichroism show that tetradecameric cpn60 can be disassembled into monomers that retain substantial secondary structure. Unfolded rhodanese induces the reassembly of tetradecameric cpn60 from monomers, and binding of rhodanese stabilizes cpn60 quaternary structure. Intermediate cpn60 species, possibly heptamers, are detected at intermediate urea concentrations after addition of unfolded rhodanese. The use of urea has demonstrated a functionally related loosening of subunit interactions in cpn60 that is not detectable under usual solution conditions. Our data suggest a highly dynamic role for the quaternary structure of cpn60 in chaperonin-mediated protein folding.