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J Biol Chem. 2012 Apr 6;287(15):11740-50. doi: 10.1074/jbc.M111.329375. Epub 2012 Feb 3.

Assembly and channel opening of outer membrane protein in tripartite drug efflux pumps of Gram-negative bacteria.

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1
Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea.

Abstract

Gram-negative bacteria are capable of expelling diverse xenobiotic substances from within the cell by use of three-component efflux pumps in which the energy-activated inner membrane transporter is connected to the outer membrane channel protein via the membrane fusion protein. In this work, we describe the crystal structure of the membrane fusion protein MexA from the Pseudomonas aeruginosa MexAB-OprM pump in the hexameric ring arrangement. Electron microscopy study on the chimeric complex of MexA and the outer membrane protein OprM reveals that MexA makes a tip-to-tip interaction with OprM, which suggests a docking model for MexA and OprM. This docking model agrees well with genetic results and depicts detailed interactions. Opening of the OprM channel is accompanied by the simultaneous exposure of a protein structure resembling a six-bladed cogwheel, which intermeshes with the complementary cogwheel structure in the MexA hexamer. Taken together, we suggest an assembly and channel opening model for the MexAB-OprM pump. This study provides a better understanding of multidrug resistance in Gram-negative bacteria.

PMID:
22308040
PMCID:
PMC3320922
DOI:
10.1074/jbc.M111.329375
[Indexed for MEDLINE]
Free PMC Article
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