Co-expression of CCT subunits hints at TRiC assembly
Oksana A Sergeeva1,2, Cameron Haase-Pettingell3,4, Jonathan A King3
1Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA. oksana.sergeeva@epfl.ch.
Cell Stress & Chaperones
|August 15, 2019
Summary
The t-complex polypeptide 1 (TCP-1) ring complex (TRiC) folds many cellular proteins. This study reveals how TRiC subunits CCT4 and CCT5 interact, suggesting CCT5 may act as a base assembly unit for TRiC formation.
Area of Science:
- Molecular biology
- Cell biology
- Protein folding
Background:
- The t-complex polypeptide 1 (TCP-1) ring complex (TRiC) is a crucial molecular chaperone in eukaryotes, essential for folding approximately 10% of cytosolic proteins.
- TRiC functions as a double-ringed barrel, with each ring comprising eight distinct chaperonin containing TCP-1 (CCT) subunits.
- Proper assembly of TRiC requires the precise incorporation of one of each CCT subunit into each ring, necessitating coordinated folding and assembly.
Purpose of the Study:
- To investigate the subunit-subunit interactions within the TRiC complex.
- To explore the assembly mechanisms of TRiC by examining the behavior of specific CCT subunits.
- To understand the role of individual CCT subunits in the formation of TRiC oligomers.
Main Methods:
- Co-expression of homo-oligomerizing CCT4 and CCT5 subunits with other CCT subunits (CCT1-8) in Escherichia coli.
- Co-expression of archaeal chaperonin Mm-Cpn (Methanococcus maripaludis chaperonin) with CCT1-8.
- Observation of interactions and formation of TRiC-like complexes and chaperonin rings.
Main Results:
- CCT5 induced the formation of double-barrel TRiC-like complexes with all CCT subunits except CCT6.
- CCT4 primarily formed chaperonin rings with CCT5 and CCT8.
- Both CCT5 and Mm-Cpn demonstrated chaperone activity by interacting with CCT subunit fragments.
Conclusions:
- Specific interactions between CCT subunits, particularly CCT5 and CCT4, suggest potential hetero-oligomer formation in TRiC assembly.
- TRiC assembly may involve subunit exchange facilitated by stable homo-oligomeric intermediates, possibly involving CCT5.
- Further analysis of CCT arrangement in different tissues and developmental stages is needed to fully elucidate TRiC assembly and subunit composition.
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