Monomeric chaperonin-60 and its 50-kDa fragment possess the ability to interact with non-native proteins, to suppress aggregation, and to promote protein folding.
Chaperonin-60 is usually isolated as a tetradecameric form arranged as two stacked seven-member rings, and this structure has been considered to be required for promoting protein folding. However, monomeric chaperonin-60 (cpn60m), isolated from holo-chaperonin of Thermus thermophilus, and its proteolytic 50-kDa fragment, which lacks amino-terminal 78 amino acid residues, can interact with non-native rhodanese and lactate dehydrogenase, suppress formation of aggregates, and promote productive folding under the appropriate conditions. However, different from tetradecameric chaperonin-60, folding promoted by cpn60m and the 50-kDa fragment produces lower yields of active enzymes and does not require ATP or chaperonin-10. These effects are not due to transient reassembly of cpn60m into a tetradecamer during the reaction, since immobilized cpn60m and the 50-kDa fragment, both of which can not reassemble into a tetradecamer, can still promote protein folding. An excess amount of the 50-kDa fragment shows an inhibitory effect on MgATP-triggered holochaperonin-dependent folding, indicating the 50-kDa fragment and holo-chaperonin can interact with the same species of non-native proteins. Thus, cpn60m has an intrinsic activity as a molecular chaperone and amino-terminal region of cpn60 is dispensable for this activity.
Taguchi
H
H
Tokyo Institute of Technology, Research Laboratory of Resources Utilization, Yokohama, Japan.
Makino
Y
Y
Yoshida
M
M
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000378:metabolism; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D018834:Chaperonin 60; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D016963:Thermus thermophilus / Q000378:metabolism*; D013884:Thiosulfate Sulfurtransferase / Q000378:metabolism*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D018834:Chaperonin 60; D006360:Heat-Shock Proteins; D010446:Peptide Fragments; D007770:L-Lactate Dehydrogenase; D013884:Thiosulfate Sulfurtransferase