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Journal of Bacteriology, July 2003, p. 4172-4185, Vol. 185, No. 14
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.14.4172-4185.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Mycobacterium tuberculosis Chaperonin 10 Heptamers Self-Associate through Their Biologically Active Loops

Michael M. Roberts,1* Alun R. Coker,2 Gianluca Fossati,3 Paolo Mascagni,3 Anthony R. M. Coates,1 and Steve P. Wood2

Medical Microbiology, Department of Cellular and Molecular Medicine, St. George's Hospital Medical School, London SW17 0RE,1 Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, England,2 Italfarmaco Research Center, 20092 Cinisello Balsamo, Milan, Italy3

Received 3 February 2003/ Accepted 24 April 2003

The crystal structure of Mycobacterium tuberculosis chaperonin 10 (cpn10Mt) has been determined to a resolution of 2.8 Å. Two dome-shaped cpn10Mt heptamers complex through loops at their bases to form a tetradecamer with 72 symmetry and a spherical cage-like structure. The hollow interior enclosed by the tetradecamer is lined with hydrophilic residues and has dimensions of 30 Å perpendicular to and 60 Å along the sevenfold axis. Tetradecameric cpn10Mt has also been observed in solution by dynamic light scattering. Through its base loop sequence cpn10Mt is known to be the agent in the bacterium responsible for bone resorption and for the contribution towards its strong T-cell immunogenicity. Superimposition of the cpn10Mt sequences 26 to 32 and 66 to 72 and E. coli GroES 25 to 31 associated with bone resorption activity shows them to have similar conformations and structural features, suggesting that there may be a common receptor for the bone resorption sequences. The base loops of cpn10s in general also attach to the corresponding chaperonin 60 (cpn60) to enclose unfolded protein and to facilitate its correct folding in vivo. Electron density corresponding to a partially disordered protein subunit appears encapsulated within the interior dome cavity of each heptamer. This suggests that the binding of substrates to cpn10 is possible in the absence of cpn60.

* Corresponding author. Mailing address: Medical Microbiology, Department of Cellular and Molecular Medicine, St. George's Hospital Medical School, Cranmer Terr., London SW17 0RE, England. Phone: 44 208 725 5722. Fax: 44 208 672 0234. E-mail: m.roberts{at}sghms.ac.uk.

Journal of Bacteriology, July 2003, p. 4172-4185, Vol. 185, No. 14
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.14.4172-4185.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Fossati, G., Izzo, G., Rizzi, E., Gancia, E., Modena, D., Moras, M. L., Niccolai, N., Giannozzi, E., Spiga, O., Bono, L., Marone, P., Leone, E., Mangili, F., Harding, S., Errington, N., Walters, C., Henderson, B., Roberts, M. M., Coates, A. R. M., Casetta, B., Mascagni, P. (2003). Mycobacterium tuberculosis Chaperonin 10 Is Secreted in the Macrophage Phagosome: Is Secretion Due to Dissociation and Adoption of a Partially Helical Structure at the Membrane?. J. Bacteriol. 185: 4256-4267 [Abstract] [Full Text]  


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