A Mycobacterium tuberculosis gene cluster encoding proteins of a phosphate transporter homologous to the Escherichia coli Pst system

Identification of a second Mycobacterium tuberculosis gene cluster encoding proteins of an ABC phosphate transporter

“…M. tuberculosis PstC-2 corresponds to a hydrophobic protein with six putative transmembrane helices, homologous to the transmembrane E. coli PstC protein [7]. Together with the previously identified homolog of the E. coli pstA, now called pstA-1 [15], these two M. tuberculosis genes constitute a new cluster of three genes distant in about 3 kb from another putative phosphate permease operon we described before [14].…”

“…1). By comparing the two M. tuberculosis proteins, PstC-1 [14] and PstC-2, 28.8% identity in a 313 aa overlap and 73.5% similarity was found. The corresponding DNA region shows 55.8% identity in a 722 nucleotides overlap.…”

“…2) [29]. Positively charged residues are found in excess at the cytoplasmic side and could [14]. The gene order in the E. coli pst operon is pstS, pstC, pstA and pstB.…”

“…The intergenic distances are indicated. C1, A1 [15] (and this article), RI (Lefbvre et al, submitted), B2 (this article), B1 [14] and AA71 [10] are the different inserts from the ~.gtll M. tuberculosis library. The M. leprae open reading frames 'phoSl', 'phoWl' and 'phoXl' found in cosmid B650 are similar to the three proteins of the operon described in this paper.…”

“…This protein has been expressed in E. coli and its affinity for the phosphate anion has been determined [13]. Recently, we demonstrated that the gene encoding this protein is part of an operon of four genes (pstB, pstS-l*, pstC-1 and pstA-2) and that phosphate uptake by whole M. boris BCG is inhibited by a monoclonal antibody directed against the PstS-I component [14]. Since the cloning and sequencing of a M. tuberculosis gene encoding the first homolog of E. coli PstA was described earlier [15] and more recently, a second PstS gene equivalent, called pstS-2, was identified in our laboratory (Lef~vre et al, submitted), we examined genomic regions surrounding these two genes attempting to identify other Pst subunits.…”