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Updated: Jul 16, 2026

In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells
Published on: September 2, 2019
The inter-ring arrangement of the cytosolic chaperonin CCT
Jaime Martín-Benito1, Julie Grantham, Jasminka Boskovic
1Centro Nacional de Biotecnología, CSIC Campus de la Universidad Autónoma de Madrid, Darwin 3, 28049 Madrid, Spain.
Abstract:
The eukaryotic cytosolic chaperonin CCT (chaperonin containing TCP-1) is the most complex of all chaperonins-an oligomeric structure built from two identical rings, each composed of single copies of eight different subunits. The arrangement of the eight subunits within each ring has been characterised for some time, but the phasing between the two rings remains unknown. Here, three-dimensional reconstructions generated by cryoelectron microscopy of complexes between CCT and either of two different monoclonal antibodies that react specifically with the CCTepsilon and CCTdelta subunits have been used to determine the phasing between the two chaperonin rings. The inter-ring arrangement is such that up/down inter-ring communication always involves two different CCT subunits in all eight positions, and the group of subunits concerned with the initiation and completion of the folding cycle cluster together both in the intra- and inter-ring arrangement. This supports a sequential mechanism of conformational changes between the two interacting rings.
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