lspA gene of Mycobacterium tuberculosis co-transcribes with Rv1540 and induced by surface and acidic stress

Lipoprotein signal peptidase, lspA (Rv1539), is the only known gene in mycobacterial genome for cleaving the signal sequence from prolipoprotein to form mature lipoprotein. It has been implicated in maintaining the virulence of Mycobacterium tuberculosis. The regulation of lspA had not been studied so far. Here, we identify a novel operon lspA-Rv1540 in M. tuberculosis. We detected co-transcription of the open reading frames of lspA-Rv1540 in in-vitro as well as in ex-vivo conditions. Analysis of the sequence upstream to lspA revealed a strong promoter activity that was shown to be induced significantly by surface stress and acidic environment.