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Substrate mutations that bypass a specific Cpn10 chaperonin requirement for protein folding
1Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland 21201, USA.
The Journal of Biological Chemistry
|December 16, 1998
Summary
Bacteriophage T4 gp31 and E. coli GroEL chaperones fold T4 major capsid protein gp23. Mutations allow gp23 to fold independently, revealing sequence-specific chaperonin requirements for protein folding.
Area of Science:
- Molecular biology
- Protein folding
- Chaperone proteins
Background:
- Bacteriophage T4 gp23 requires chaperones for proper folding and capsid assembly.
- The T4 GroES homologue, gp31, works with E. coli GroEL to facilitate this process.
- E. coli GroES is not a functional co-chaperonin for gp23 folding.
Purpose of the Study:
- Investigate the role of specific sequence determinants in gp23 folding.
- Characterize mutations conferring chaperonin-independent folding.
- Determine the specificity of co-chaperonin interactions in protein folding.
Main Methods:
- In vivo expression studies
- Sequencing and characterization of gp23 mutations
- Site-directed mutagenesis
- Polyhead reassembly experiments
Main Results:
- gp23 folding is dependent on the gp31-GroEL chaperonin system.
- Mutations in gp23 enable chaperonin-independent folding by altering specific sequence regions.
- Conservative amino acid substitutions confer a bypass phenotype, though with reduced efficiency.
- gp31 is not essential for gp23 binding to GroEL.
- GroEL-GroES does not enhance folding of mutated gp23.
Conclusions:
- Chaperonin requirements for gp23 folding are determined by specific sequence elements.
- Mutations confer a chaperonin bypass phenotype through additive effects on critical regions.
- Results suggest co-chaperonin specificity in the folding of certain protein substrates.