Abstract
Mycobacterium tuberculosis, the causative agent of tuberculosis remains a global health concern, further compounded by the high rates of HIV-TB co-infection and emergence of multi- and extensive drug resistant TB, all of which have hampered efforts to eradicate this disease. As a result, novel anti-tubercular interventions are urgently required, with the peptidoglycan component of the M. tuberculosis cell wall emerging as an attractive drug target. Peptidoglycan M23 endopeptidases can function as active cell wall hydrolases or degenerate activators of hydrolases in a variety of bacteria, contributing to important processes such as bacterial growth, division and virulence. Herein, we investigate the function of the Rv0950-encoded putative M23 endopeptidase in M. tuberculosis. In silico analysis revealed that this protein is conserved in mycobacteria, with a zinc-binding catalytic site predictive of hydrolytic activity. Transcript analysis indicated that expression of Rv0950c was elevated during lag and log phases of growth and reduced in stationary phase. Deletion of Rv0950c yielded no defects in growth, colony morphology, antibiotic susceptibility or intracellular survival but caused a reduction in cell length. Staining with a monopeptide-derived fluorescent D-amino acid, which spatially reports on sites of active PG biosynthesis or repair, revealed an overall reduction in uptake of the probe in ΔRv0950c. When stained with a dipeptide probe in the presence of cell wall damaging agents, the ΔRv0950c mutant displayed reduced sidewall labelling. As bacterial peptidoglycan metabolism is important for survival and pathogenesis, the role of Rv0950c and other putative M23 endopeptidases in M. tuberculosis should be explored further.
Highlights
Tuberculosis (TB), caused by Mycobacterium tuberculosis infection, has surpassed HIV/AIDS as the leading cause of death by an infectious disease globally [1]
Rv0950c is the only homologue of the three M. tuberculosis homologues that is conserved in M. leprae (S6 Table, S3 Fig), which retains the minimal genome required for virulence [48]
M23 endopeptidases represent a class of highly versatile enzymes required for growth and/or virulence of pathogenic bacteria [21,45,47,63] these proteins remain unexplored in M. tuberculosis
Summary
Tuberculosis (TB), caused by Mycobacterium tuberculosis infection, has surpassed HIV/AIDS as the leading cause of death by an infectious disease globally [1]. Rates of decline in TB incidence are insufficient to reach the ambitious targets set by the World Health. An M23-domain containing protein in M. tuberculosis. National Health Scholars Grant from the South African Medical Research Council with funds from the Department of Health, and a Medical Research Endowment grant from the Wits University Faculty of Health Sciences Research Office.
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