Molecular Determinants for OMF Selectivity in Tripartite RND Multidrug Efflux Systems

• Main Authors: Esther Boyer (Author), Jean Dessolin (Author), Margaux Lustig (Author), Marion Decossas (Author), Gilles Phan (Author), Quentin Cece (Author), Grégory Durand (Author), Véronique Dubois (Author), Joris Sansen (Author), Jean-Christophe Taveau (Author), Isabelle Broutin (Author), Laetitia Daury (Author), Olivier Lambert (Author)
• Format: Book
• Published: MDPI AG, 2022-01-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

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 <i>Pseudomonas aeruginosa</i> and <i>Escherichia coli</i>, 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_Q93R-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_Q93R 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_Q93R. 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.

Item Description

10.3390/antibiotics11020126
2079-6382