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Updated: Aug 11, 2026
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Escherichia coli -Based Complementation Assay to Study the Chaperone Function of Heat Shock Protein 70
Published on: March 8, 2024
Mycobacterium tuberculosis expresses two chaperonin-60 homologs
T H Kong1, A R Coates, P D Butcher
1Department of Medical Microbiology, St. George's Hospital Medical School, London, United Kingdom.
Summary
Mycobacterium tuberculosis possesses two chaperonin-60 (Cpn60) genes. A newly identified Cpn60-1 gene, located near the 10-kDa antigen gene, is expressed as a 60-kDa protein, distinct from the known 65-kDa Cpn60-2 antigen.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Mycobacterium tuberculosis, the bacterium causing tuberculosis, expresses immunodominant 65-kDa and 10-kDa proteins.
- The 65-kDa protein is homologous to chaperonin-60 (Cpn60) heat shock proteins (HSPs), and the 10-kDa protein to chaperonin-10 (Cpn10) HSPs.
- These two proteins are encoded by distinct genes in M. tuberculosis.
Purpose of the Study:
- To investigate the presence and characteristics of additional Cpn60 homologs in M. tuberculosis.
- To determine the genetic organization and expression of a newly identified Cpn60 homolog.
Main Methods:
- Bioinformatic analysis to identify homologous sequences.
- Gene mapping to determine the location of the second Cpn60 homolog.
- Primer-extension analysis to identify transcription start sites.
- Protein purification and characterization.
Main Results:
- A second Cpn60 homolog, designated Cpn60-1, was identified 98 bp downstream of the 10-kDa antigen gene.
- Cpn60-1 shares 61% amino acid identity with the previously identified 65-kDa Cpn60-2 antigen.
- Primer-extension and protein purification confirmed that the cpn60-1 gene is transcribed and expressed as an approximately 60-kDa polypeptide.
Conclusions:
- M. tuberculosis contains at least two distinct Cpn60 genes, Cpn60-1 and Cpn60-2.
- The Cpn60-1 gene is expressed and produces a protein of similar size to the known Cpn60-2 antigen.
- The discovery of a second Cpn60 homolog provides new insights into the molecular mechanisms and immune response related to tuberculosis.
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