A small-molecule inhibitor of BamA impervious to efflux and the outer membrane permeability barrier.

TitleA small-molecule inhibitor of BamA impervious to efflux and the outer membrane permeability barrier.
Publication TypeJournal Article
Year of Publication2019
AuthorsHart, EM, Mitchell, AM, Konovalova, A, Grabowicz, M, Sheng, J, Han, X, Rodriguez-Rivera, FP, Schwaid, AG, Malinverni, JC, Balibar, CJ, Bodea, S, Si, Q, Wang, H, Homsher, MF, Painter, RE, Ogawa, AK, Sutterlin, H, Roemer, T, Black, TA, Rothman, DM, Walker, SS, Silhavy, TJ
JournalProc Natl Acad Sci U S A
Date Published2019 Oct 22
KeywordsAnti-Bacterial Agents, Bacterial Outer Membrane Proteins, Biological Transport, Cell Membrane, Cell Membrane Permeability, Drug Evaluation, Preclinical, Drug Resistance, Bacterial, Escherichia coli, Escherichia coli Proteins, Microbial Sensitivity Tests, Protein Multimerization, Triazines

<p>The development of new antimicrobial drugs is a priority to combat the increasing spread of multidrug-resistant bacteria. This development is especially problematic in gram-negative bacteria due to the outer membrane (OM) permeability barrier and multidrug efflux pumps. Therefore, we screened for compounds that target essential, nonredundant, surface-exposed processes in gram-negative bacteria. We identified a compound, MRL-494, that inhibits assembly of OM proteins (OMPs) by the β-barrel assembly machine (BAM complex). The BAM complex contains one essential surface-exposed protein, BamA. We constructed a mutagenesis library, screened for resistance to MRL-494, and identified the mutation BamA restores OMP biogenesis in the presence of MRL-494. The mutant protein has both altered conformation and activity, suggesting it could either inhibit MRL-494 binding or allow BamA to function in the presence of MRL-494. By cellular thermal shift assay (CETSA), we determined that MRL-494 stabilizes BamA and BamA from thermally induced aggregation, indicating direct or proximal binding to both BamA and BamA Thus, it is the altered activity of BamA responsible for resistance to MRL-494. Strikingly, MRL-494 possesses a second mechanism of action that kills gram-positive organisms. In microbes lacking an OM, MRL-494 lethally disrupts the cytoplasmic membrane. We suggest that the compound cannot disrupt the cytoplasmic membrane of gram-negative bacteria because it cannot penetrate the OM. Instead, MRL-494 inhibits OMP biogenesis from outside the OM by targeting BamA. The identification of a small molecule that inhibits OMP biogenesis at the cell surface represents a distinct class of antibacterial agents.</p>

Alternate JournalProc Natl Acad Sci U S A
PubMed ID31591200
PubMed Central IDPMC6815139
Grant ListR35 GM118024 / GM / NIGMS NIH HHS / United States