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Nat. Commun., 29 May 2026 | https://doi.org/10.1038/s41467-026-73864-w Secretin-interacting plug proteins prevent antibiotic influx during type IV pilus assembly in Pseudomonas aeruginosa

Oh Hyun Kwon^1,2†, Yeseul Lee^2†, Bumhan Ryu^3†, Joel W Sher⁴, Sohee Park¹, Frédéric Lauber^5,6, Bi-o Kim¹, Youngki Yoo⁷, Seung-Hyun Cho^5,6, Donghui Choe¹, You-Hee Cho⁸, Jean François Collet^5,6, Melanie D Ohi^7,9, Thomas G Bernhardt^4,10, Jeong Min Chung^2*, and Hongbaek Cho^1*

¹Department of Biological Sciences, College of Natural Sciences, Sungkyunkwan University, Suwon 16419, Republic of Korea
²Department of Biotechnology, The Catholic University of Korea, Bucheon 14662, Republic of Korea
³Research Solution Center, Institute for Basic Science, Daejeon 34126, Republic of Korea
⁴Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
⁵WELBIO Department, WEL Research Institute, Avenue Pasteur, 6, 1300 Wavre, Belgium
⁶de Duve Institute, Université catholique de Louvain (UCLouvain), Avenue Hippocrate 75, 1200 Brussels, Belgium
⁷Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA.
⁸Department of Pharmacy, College of Pharmacy and Institute of Pharmaceutical Sciences CHA University, Republic of Korea
⁹Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA.
¹⁰Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA

^*To whom correspondence should be addressed. : Hongbaek Cho, Ph.D., Jeong Min Chung, Ph.D.
^†contributed equally

Abstract

Type IV pili (T4P) are important virulence factors that mediate host attachment and other pathogenic functions. In Gram-negative bacteria, T4P are assembled from pilin subunits at the inner membrane (IM) and extend through the outer membrane (OM) via secretin channels. Although essential for T4P function, secretin complexes can impair the OM permeability barrier, potentially allowing entry of toxic compounds. The mechanisms that prevent such influx remain poorly understood. Here, we identify SlkA and SlkB (PA5122 and PA5123) as periplasmic proteins that interact with the T4P secretin channel and block antibiotic influx. Our data indicate that these proteins function as physical plugs sealing the channel until the IM complex docks and pilus assembly begins. These findings demonstrate that Slk proteins and the IM complex function redundantly to maintain OM barrier integrity, and that their interaction with the secretin channel represents a promising target for antibiotic potentiation.

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