A diverse family of protein antibiotics inhibits the BAM complex by β-signal mimicry
- 1Monash University
Abstract
Lectin-like protein antibiotics (Llps) kill Pseudomonas by inhibiting BamA, the essential core of the beta-barrel assembly machinery (BAM). Llps are composed of one or two beta;-lectin domains and a C-terminal peptide, with characterisation to date centred on the two-domain L-type pyocins of P. aeruginosa, which bind BamA extracellular loop 6 and inhibit by delivering the C-terminal peptide to BamA beta;-strand 1. Whether this mechanism is general, and how Llps contend with BamA sequence differences across species, remained unknown. We screened 238 Pseudomonas Llps against 101 genome-sequenced isolates, showing susceptibility across the family is set by BamA extracellular loop 6. Loop 6 length varies, and Llps fall into three targeting modes: short-loop and long-loop specialists and broad-range dual targeters, which have arisen repeatedly. We determine the 2.66 angstrom cryo-electron microscopy structure of a two-domain LlpA bound to BAM, showing recognition has been relocated relative to the L-type pyocins, with loop 6 bound by a single face of the N-terminal beta-lectin domain rather than the inter-domain cleft. This explains how single-domain LlpBs retain BamA targeting and why the second lectin domain has been lost at least twice. We show that the BamA inhibition mechanism is shared across Llps, with a hypervariable C-terminal peptide binding BamA beta-strand 1, inhibiting the BAM insertase by mimicking the beta-signal of BamA substrates. Together, these data provide an atlas of Llp diversity and the mechanistic principles for engineering it, identifying Llps as a tuneable, multi-interface scaffold for BAM-directed precision antibacterials against pathogenic Pseudomonas, including economically important plant pathogens.
Related
- Conserved mycobacteriophage protein uses structural mimicry to displace host initiation factors
- PBT2 potentiates carbapenem antibiotics against diverse Klebsiella pneumoniae strains
- DyME: An MD-based engine exploiting HTP mutagenesis for protein engineering and recognition mimicry
- Differential impact of cell wall antibiotics on the Rod complex and aPBPs in Bacillus subtilis: Insights into the peptidoglycan elongation machineries
- Surfactant Protein A Inhibits Human Rhinovirus C Binding and Infection of Airway Epithelial Cells from Pediatric Asthma
BibTeX
@misc{munder2026diverse,
title = {{A diverse family of protein antibiotics inhibits the BAM complex by β-signal mimicry}},
author = {F. Munder and C. Wang and L. Jimenez and M. T. Doyle and J. P. Connolly and G. J. Knott and R. Grinter},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.25.754295},
url = {https://www.biorxiv.org/content/10.64898/2026.09.25.754295v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - A diverse family of protein antibiotics inhibits the BAM complex by β-signal mimicry
AU - F. Munder
AU - C. Wang
AU - L. Jimenez
AU - M. T. Doyle
AU - J. P. Connolly
AU - G. J. Knott
AU - R. Grinter
PY - 2026
DA - 2026/09/25
PB - bioRxiv
DO - 10.64898/2026.09.25.754295
UR - https://www.biorxiv.org/content/10.64898/2026.09.25.754295v1
AB - Lectin-like protein antibiotics (Llps) kill Pseudomonas by inhibiting BamA, the essential core of the beta-barrel assembly machinery (BAM). Llps are composed of one or two beta;-lectin domains and a C-terminal peptide, with characterisation to date centred on the two-domain L-type pyocins of P. aeruginosa, which bind BamA extracellular loop 6 and inhibit by delivering the C-terminal peptide to BamA beta;-strand 1. Whether this mechanism is general, and how Llps contend with BamA sequence differences across species, remained unknown. We screened 238 Pseudomonas Llps against 101 genome-sequenced isolates, showing susceptibility across the family is set by BamA extracellular loop 6. Loop 6 length varies, and Llps fall into three targeting modes: short-loop and long-loop specialists and broad-range dual targeters, which have arisen repeatedly. We determine the 2.66 angstrom cryo-electron microscopy structure of a two-domain LlpA bound to BAM, showing recognition has been relocated relative to the L-type pyocins, with loop 6 bound by a single face of the N-terminal beta-lectin domain rather than the inter-domain cleft. This explains how single-domain LlpBs retain BamA targeting and why the second lectin domain has been lost at least twice. We show that the BamA inhibition mechanism is shared across Llps, with a hypervariable C-terminal peptide binding BamA beta-strand 1, inhibiting the BAM insertase by mimicking the beta-signal of BamA substrates. Together, these data provide an atlas of Llp diversity and the mechanistic principles for engineering it, identifying Llps as a tuneable, multi-interface scaffold for BAM-directed precision antibacterials against pathogenic Pseudomonas, including economically important plant pathogens.
ER -