Target-based screen against a periplasmic serine protease that regulates intrabacterial pH homeostasis in Mycobacterium tuberculosis

ACS Chem Biol. 2015 Feb 20;10(2):364-71. doi: 10.1021/cb500746z. Epub 2014 Dec 5.

Abstract

Mycobacterium tuberculosis (Mtb) maintains its intrabacterial pH (pHIB) near neutrality in the acidic environment of phagosomes within activated macrophages. A previously reported genetic screen revealed that Mtb loses this ability when the mycobacterial acid resistance protease (marP) gene is disrupted. In the present study, a high throughput screen (HTS) of compounds against the protease domain of MarP identified benzoxazinones as inhibitors of MarP. A potent benzoxazinone, BO43 (6-chloro-2-(2'-methylphenyl)-4H-1,3-benzoxazin-4-one), acylated MarP and lowered Mtb's pHIB and survival during incubation at pH 4.5. BO43 had similar effects on MarP-deficient Mtb, suggesting the existence of additional target(s). Reaction of an alkynyl-benzoxazinone, BO43T, with Mycobacterium bovis variant bacille Calmette-Guérin (BCG) followed by click chemistry with azido-biotin identified both the MarP homologue and the high temperature requirement A1 (HtrA1) homologue, an essential protein. Thus, the chemical probe identified through a target-based screen not only reacted with its intended target in the intact cells but also implicated an additional enzyme that had eluded a genetic screen biased against essential genes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Benzoxazines / chemistry
  • Benzoxazines / pharmacology
  • Gene Expression Regulation, Bacterial / physiology
  • Gene Expression Regulation, Enzymologic / physiology
  • Homeostasis*
  • Hydrogen-Ion Concentration
  • Molecular Probes / chemistry
  • Molecular Probes / metabolism
  • Molecular Structure
  • Mycobacterium tuberculosis / cytology
  • Mycobacterium tuberculosis / enzymology*
  • Mycobacterium tuberculosis / genetics
  • Mycobacterium tuberculosis / metabolism*
  • Periplasm / enzymology*
  • Serine Proteases / genetics
  • Serine Proteases / metabolism*
  • Serine Proteinase Inhibitors / chemistry
  • Serine Proteinase Inhibitors / pharmacology

Substances

  • Bacterial Proteins
  • Benzoxazines
  • Molecular Probes
  • Serine Proteinase Inhibitors
  • Serine Proteases