title: Mycobacterium tuberculosis chaperonin 10 forms stable tetrameric and heptameric structures. Implications for its diverse biological activities.
abstract: The chaperonin activity of sequence-related chaperonin 10 proteins requires their aggregation into heptameric structures. We describe size-exclusion chromatography and ultracentrifugation studies that reveal that while Escherichia coli chaperonin 10 exists as a heptamer, the Mycobacterium tuberculosis chaperonin 10 is tetrameric in dilute solutions and in whole M. tuberculosis lysate. At high protein concentration and in the presence of saturating amounts of divalent ions, the protein is heptameric. Human chaperonin 10 is predominantly heptameric, although smaller oligomers were detected. These differences in structural assembly between species may explain differences in biological activity such as antigenicity. Using C-terminal and N-terminal fragments, sequence 1-25 was identified as indispensable for aggregation. CD spectroscopy studies revealed that (i) a minimum at 202-204 nm correlates with aggregation and characterizes not only the spectrum of the mycobacterial protein, but also those of E. coli and human chaperonin 10 proteins; (ii) the interactions between subunits are of the hydrophobic type; and (iii) the anti-parallel beta-pleated sheet is the main secondary structure element of subunits in both tetrameric and heptameric proteins.
authors.affiliation: Department of Chemistry, Italfarmaco Research Centre, Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Fossati
authors.forename: P
authors.initials: P
authors.lastname: Lucietto
authors.forename: P
authors.initials: P
authors.lastname: Giuliani
authors.forename: A R
authors.initials: AR
authors.lastname: Coates
authors.forename: S
authors.initials: S
authors.lastname: Harding
authors.forename: H
authors.initials: H
authors.lastname: Cölfen
authors.forename: G
authors.initials: G
authors.lastname: Legname
authors.forename: E
authors.initials: E
authors.lastname: Chan
authors.forename: A
authors.initials: A
authors.lastname: Zaliani
authors.forename: P
authors.initials: P
authors.lastname: Mascagni
mesh_terms: D000595:Amino Acid Sequence; D018835:Chaperonin 10 / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D018835:Chaperonin 10; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011994:Recombinant Proteins