Sequential ATP-induced allosteric transitions of the cytoplasmic chaperonin containing TCP-1 revealed by EM analysis.
The eukaryotic cytoplasmic chaperonin containing TCP-1 (CCT) is a hetero-oligomeric complex that assists the folding of actins, tubulins and other proteins in an ATP-dependent manner. To understand the allosteric transitions that occur during the functional cycle of CCT, we imaged the chaperonin complex in the presence of different ATP concentrations. Labeling by monoclonal antibodies that bind specifically to the CCTalpha and CCTdelta subunits enabled alignment of all the CCT subunits of a given type in different particles. The analysis shows that the apo state of CCT has considerable apparent conformational heterogeneity that decreases with increasing ATP concentration. In contrast with the concerted allosteric switch of GroEL, ATP-induced conformational changes in CCT are found to spread around the ring in a sequential fashion that may facilitate domain-by-domain substrate folding. The approach described here can be used to unravel the allosteric mechanisms of other ring-shaped molecular machines.
Rivenzon-Segal
Dalia
D
Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
Wolf
Sharon G
SG
Shimon
Liat
L
Willison
Keith R
KR
Horovitz
Amnon
A
D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D000495:Allosteric Site; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002417:Cattle; D018834:Chaperonin 60 / Q000737:chemistry / Q000378:metabolism; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D013379:Substrate Specificity
D000906:Antibodies; D018834:Chaperonin 60; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins