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J. Bacteriol., May 1997, 2900-2906, Vol 179, No. 9
P Lefevre, M Braibant, L de Wit, M Kalai, D Roeper, J Grotzinger, JP Delville, P Peirs, J Ooms, K Huygen and J Content
A gene encoding a protein homologous to the periplasmic ABC phosphate
binding receptor PstS from Escherichia coli was cloned and sequenced from a
lambda gt11 library of Mycobacterium tuberculosis by screening with
monoclonal antibody 2A1-2. Its degree of similarity to the E. coli PstS is
comparable to those of the previously described M. tuberculosis phosphate
binding protein pab (Ag78, Ag5, or 38-kDa protein) and another M.
tuberculosis protein which we identified recently. We suggest that the
three M. tuberculosis proteins share a similar function and could be named
PstS-1, PstS-2, and PstS-3, respectively. Molecular modeling of their
three-dimensional structures using the structure of the E. coli PstS as a
template and their inducibility by phosphate starvation support this view.
Recombinant PstS-2 and PstS-3 were produced and purified by affinity
chromatography. With PstS-1, these proteins were used to demonstrate the
specificity of three groups of monoclonal antibodies. Using these
antibodies in flow cytometry and immunoblotting analyses, we demonstrate
that the three genes are expressed and their protein products are present
and accessible at the mycobacterial surface as well as in its culture
filtrate. Together with the M. tuberculosis genes encoding homologs of the
PstA, PstB, and PstC components we cloned before, the present data suggest
that at least one, and possibly several, related and functional ABC
phosphate transporters exist in mycobacteria. It is hypothesized that the
mycobacterial gene duplications presented here may be a subtle adaptation
of intracellular pathogens to phosphate starvation in their alternating
growth environments.
Copyright © 1997, American Society for Microbiology
Three different putative phosphate transport receptors are encoded by the Mycobacterium tuberculosis genome and are present at the surface of Mycobacterium bovis BCG
Department of Virology, Institut Pasteur, Brussels, Belgium.
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