Chalkophore mediated respiratory oxidase flexibility and M. tuberculosis virulence

About This Grant

PROJECT SUMMARY Chalkophore mediated respiratory oxidase flexibility and M. tuberculosis virulence Diisonitrile lipopeptides are a novel class of copper-chelating natural products that are biosynthesized by non- ribosomal peptide synthetases found in a variety of Actinobacteria, including Mycobacterium tuberculosis, the bacteria that cause tuberculosis. In multiple studies, genetic disruption of the M. tuberculosis diisonitrile biosynthetic gene cluster attenuates bacterial virulence in mouse models of tuberculosis. This copper-binding activity identifies the diisonitriles as `chalkophores', which are structurally distinct from the well-known methanobactin chalkophores in methanotrophs. Further, we have shown that M. tuberculosis mutants in which chalkophore biosynthesis is disrupted are defective for growth in low-copper or copper-chelated media, and that this defect can be rescued by treatment with exogenous, synthetic diisonitriles, consistent with a role for diisonitriles in copper uptake. We have also shown that the diisonitrile chalkophore system is required to maintain the function of the copper-containing respiratory oxidase in low-copper culture and in mouse infection, establishing a specific physiologic target for diisonitrile chalkophore function and defining chalkophore mediated respiratory oxidase flexibility as an important virulence determine of M. tuberculosis. Further, the host immune pressure that targets M. tuberculosis respiration is independent of adaptive immunity. Building upon this work, in this proposal we will discover and characterize components of the chalkophore biosynthetic and handling systems using genetic, chemical biologic, and proteomic approaches. We will define the metal responsive transcriptional switch that controls respiratory oxidase flexibility and define the host pathways that target Mtb respiration during infection. This project will be carried out through a multidisciplinary collaboration led by Michael Glickman and Derek Tan comprising combined expertise in organic synthesis, organometallic chemistry, chemical biology, molecular biology, proteomics and microbial pathogenesis. Our long-term goals are to elucidate the roles of chalkophore mediated respiratory oxidase flexibility in M. tuberculosis pathogenesis and to understand the host factors that target the metal centers of the bacterial respiratory chain.