Molecular Determinants for OMF Selectivity in Tripartite RND Multidrug Efflux Systems

• Published in: Antibiotics (Basel) Vol. 11; no. 2; p. 126
• Main Authors: Boyer, Esther, Dessolin, Jean, Lustig, Margaux, Decossas, Marion, Phan, Gilles, Cece, Quentin, Durand, Grégory, Dubois, Véronique, Sansen, Joris, Taveau, Jean-Christophe, Broutin, Isabelle, Daury, Laetitia, Lambert, Olivier
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01-01-2022; MDPI
• Subjects: Amino acids; Antibiotic resistance; Antibiotics; Bacteriology; Biochemistry, Molecular Biology; Biosensors; Carbenicillin; Cell division; Cell walls; Drug resistance in microorganisms; E coli; Efflux; efflux pump; Electron microscopy; Experiments; Interferometry; Life Sciences; Membranes; Microbiology and Parasitology; Microscopy; Mutation; Pharmaceutical sciences; Pharmacology; Proteins; Pseudomonas aeruginosa; RND; Selectivity; Strain analysis; Structural Biology; Ticarcillin; France; efflux pump; antibiotic resistance; RND
• ISSN: 2079-6382; 2079-6382
• DOI: 10.3390/antibiotics11020126

Tripartite multidrug RND efflux systems made of an inner membrane transporter, an outer membrane factor (OMF) and a periplasmic adaptor protein (PAP) form a canal to expel drugs across Gram-negative cell wall. Structures of MexA-MexB-OprM and AcrA-AcrB-TolC, from
and
, respectively, depict a reduced interfacial contact between OMF and PAP, making unclear the comprehension of how OMF is recruited. Here, we show that a Q93R mutation of MexA located in the α-hairpin domain increases antibiotic resistance in the MexA
-MexB-OprM-expressed strain. Electron microscopy single-particle analysis reveals that this mutation promotes the formation of tripartite complexes with OprM and non-cognate components OprN and TolC. Evidence indicates that MexA
self-assembles into a hexameric form, likely due to interprotomer interactions between paired R93 and D113 amino acids. C-terminal deletion of OprM prevents the formation of tripartite complexes when mixed with MexA and MexB components but not when replacing MexA with MexA
. This study reveals the Q93R MexA mutation and the OprM C-terminal peptide as molecular determinants modulating the assembly process efficacy with cognate and non-cognate OMFs, even though they are outside the interfacial contact. It provides insights into how OMF selectivity operates during the formation of the tripartite complex.