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The Mycobacterium tuberculosis exported repetitive protein (RvErp) is a crucial virulence-associated factor as determined by its role in the survival and multiplication of mycobacteria in cultured macrophages and in vivo. Although attempts have been made to understand the function of Erp protein, its exact role in Mycobacterium pathogenesis is still elusive. One way to determine this is by searching for novel interactions of RvErp. Using a yeast two-hybrid assay, an adenylyl cyclase (AC), Rv2212, was found to interact with RvErp. The interaction between RvErp and Rv2212 is direct and occurs at the endogenous level. The Erp protein of Mycobacterium smegmatis (MSMEG_6405, or MsErp) interacts neither with Rv2212 nor with Ms_4279, the M. smegmatis homologue of Rv2212. Deletion mutants of Rv2212 revealed its adenylyl cyclase domain to be responsible for the interaction. RvErp enhances Rv2212-mediated cyclic AMP (cAMP) production. Also, the biological significance of the interaction between RvErp and Rv2212 was demonstrated by the enhanced survival of M. smegmatis within THP-1 macrophages. Taken together, these studies address a novel mechanism by which Erp executes its function. IMPORTANCE RvErp is one of the important virulence factors of M. tuberculosis. This study describes a novel function of RvErp protein of M. tuberculosis by identifying Rv2212 as its interacting protein.Rv2212 is an adenylyl cyclase (AC) and produces cAMP, one of the prime second messengers that regulate the intracellular survival of mycobacteria. Therefore, the significance of investigating novel interactions of RvErp is paramount in unraveling the mechanisms governing the intracellular survival of mycobacteria. Discerning the molecular mechanisms used by specific mycobacterial proteins involved in infection and virulence requires an understanding of the protein-protein interaction network. The interactions of secretory proteins of Mycobacterium with the host machinery are vital for successful infection. One such secretory protein involved in virulence of Mycobacterium tuberculosis is Erp (Rv3810).The erp gene of M. tuberculosis encodes an ϳ28.0-kDa secretory protein that migrates as a 36.0-kDa protein and is present in all species of mycobacteria. Its disruption results in a marked decrease in virulence, with lower levels of survival not only in in vitro and cell culture assays but also under in vivo conditions (1, 2). It was recently shown that the nature of the erp allele strongly affects the number and the size of the lung lesions in infected animals (3). No homologue of Erp has been found in other bacterial species, making Erp a mycobacterial signature (4).Erp has a composite structure made up of three domains. While the amino-terminal domain (amino acids 1 to 80) and the carboxyterminal domain (amino acids 176 to 284) are conserved, the central domain, consisting of tandem repeats of 5 amino acids based on a PGLTS motif, is subjected to a high level of interspecies variability (1). A signal sequence is present in the amino termi...

Introduction The mechanistic details of first line drug (FLD) resistance have been thoroughly explored but the genetic resistance mechanisms of second line injectables, which form the backbone of the combinatorial drug resistant tuberculosis therapy, are partially identified. This study aims to highlight the genetic and spoligotypic differences in the second line drug (SLD) resistant and sensitive Mycobacterium tuberculosis ( Mtb) clinical isolates from Mumbai (Western India) and Lucknow (Northern India). Methods The rrs, eis, whiB7, tlyA, gyrA and gyrB target loci were screened in 126 isolates and spoligotyped. Results The novel mutations were observed in whiB7 loci (A43T, C44A, C47A, G48T, G59A and T152G in 5’-UTR; A42C, C253T and T270G in gene), tlyA (+CG200, G165A, C415G, and +G543) and gyrB (+G1359 and +A1429). Altogether, the rrs, eis , and whiB7 loci harbored mutations in ~86% and ~47% kanamycin resistant isolates from Mumbai and Lucknow, respectively. Mumbai strains displayed higher prevalence of mutations in gyrA (~85%) and gyrB loci (~13%) as compared to those from Lucknow (~69% and ~3.0%, respectively). Further, spoligotyping revealed that Beijing lineage is distributed equally amongst the drug resistant strains of Mumbai and Lucknow, but EAI-5 is existed at a higher level only in Mumbai. The lineages Manu2, CAS1-Delhi and T1 are more prevalent in Lucknow. Conclusion Besides identifying novel mutations in whiB7, tlyA and gyrB target loci, our analyses unveiled a potential polymorphic and phylogeographical demarcation among two distinct regions.