Bypassing BamD Essentiality by Mutations in a Non-essential Substrate

Authors

Santosh Kumar
Anna Konovalova

Language

English

Publication Date

9-10-2025

Journal

mBio

DOI

10.1128/mbio.01769-25

PMID

40823823

PMCID

PMC12421809

PubMedCentral® Posted Date

8-18-2025

PubMedCentral® Full Text Version

Post-print

Abstract

The β-barrel assembly machinery (Bam) is essential for assembling all transmembrane β-barrel outer membrane proteins in gram-negative bacteria. The Bam complex consists of the central β-barrel protein BamA and accessory Bam lipoproteins, including the widely conserved and essential BamD. BamD is assumed to be an essential regulator of OMP assembly, as its absence causes a global defect in OMP biogenesis. Here, we challenge this view by demonstrating that BamD essentiality is both conditional and substrate specific. In Escherichia coli, its function can be bypassed by preventing BamA jamming by a single, non-essential substrate RcsF. Our findings suggest that BamD plays two distinct roles in the Bam complex. It prevents improper RcsF engagement that can jam BamA, and it kinetically enhances BamA-mediated OMP assembly. Contrary to prevailing models, we demonstrate that the second function in general OMP assembly is not essential. We report a genetic background in which each Bam lipoprotein is dispensable for viability, providing a powerful new system for investigating their functions in OMP assembly in the context of unmodified, wild-type BamA.

Keywords

Escherichia coli Proteins, Bacterial Outer Membrane Proteins, Escherichia coli, Mutation, Lipoproteins, gram-negative bacteria, outer membrane biogenesis, Bam complex, protein folding

Published Open-Access

yes

Recommended Citation

Santosh Kumar and Anna Konovalova, "Bypassing BamD Essentiality by Mutations in a Non-essential Substrate" (2025). Faculty, Staff and Student Publications. 6004.
https://digitalcommons.library.tmc.edu/uthgsbs_docs/6004