9sgt
S315G KatG mutant one Heme
Structural highlights
FunctionKATG_MYCTU Bifunctional enzyme with both catalase and broad-spectrum peroxidase activity. Displays also NADH oxidase, isoniazid (INH) lyase and isonicotinoyl-NAD synthase activity. May play a role in the intracellular survival of mycobacteria. May be involved in DNA repair. Partly complements recA-deficient E.coli cells exposed to UV radiation, mitomycin C or hydrogen peroxide. Increases resistance to mitomycin C in E.coli cells deficient for either uvrA, uvrB or uvrC.[1] Publication Abstract from PubMedMycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is responsible for a global health burden affecting over a quarter of the world's population. The increasing prevalence of drug-resistant TB poses a significant threat to current treatment strategies. Isoniazid (INH) is a first-line prodrug used in TB therapy, which requires activation by the catalase-peroxidase enzyme KatG. Upon activation, INH inhibits InhA, thereby disrupting mycolic acid biosynthesis, a crucial process for maintaining Mtb's distinctive, lipid-rich cell wall. The most common naturally occurring resistance-associated mutation in KatG is S315T, though other variants at this position, such as S315G, S315N, S315I, and S315R, have also been reported. In this study, we employ cryo-electron microscopy (cryo-EM) to investigate the structural basis of INH resistance conferred by these KatG variants. We present high-resolution cryo-EM structures that reveal heterogeneity in heme loading among the mutants. Detailed structural analysis highlights alterations in the hydrogen-bonding network and substrate access channel unique to each variant, offering direct comparisons with the wild-type (WT) KatG protein. Our findings provide a molecular explanation for clinical INH resistance and lay the groundwork for the rational design of next-generation anti-TB therapeutics. Uncovering the structural impact of KatG Ser315 mutations in Mycobacterium tuberculosis via cryo-EM.,Allport T, Chaplin AK Protein Sci. 2026 Jan;35(1):e70409. doi: 10.1002/pro.70409. PMID:41432360[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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