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Structure. 2018 May 1;26(5):708-721.e4. doi: 10.1016/j.str.2018.03.010. Epub 2018 Apr 12.

Unusual Constriction Zones in the Major Porins OmpU and OmpT from Vibrio cholerae.

Author information

1
Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle Upon Tyne NE2 4HH, UK.
2
Department of Physics, University of Cagliari, Monserrato, Cagliari, Italy.
3
Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany.
4
Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle Upon Tyne NE2 4HH, UK. Electronic address: bert.van-den-berg@ncl.ac.uk.

Abstract

The outer membranes (OM) of many Gram-negative bacteria contain general porins, which form nonspecific, large-diameter channels for the diffusional uptake of small molecules required for cell growth and function. While the porins of Enterobacteriaceae (e.g., E. coli OmpF and OmpC) have been extensively characterized structurally and biochemically, much less is known about their counterparts in Vibrionaceae. Vibrio cholerae, the causative agent of cholera, has two major porins, OmpU and OmpT, for which no structural information is available despite their importance for the bacterium. Here we report high-resolution X-ray crystal structures of V. cholerae OmpU and OmpT complemented with molecular dynamics simulations. While similar overall to other general porins, the channels of OmpU and OmpT have unusual constrictions that create narrower barriers for small-molecule permeation and change the internal electric fields of the channels. Together with electrophysiological and in vitro transport data, our results illuminate small-molecule uptake within the Vibrionaceae.

KEYWORDS:

OmpT; OmpU; Vibrio cholerae; bile salts; crystal structure; electrophysiology; membrane channel; outer membrane protein; porin

PMID:
29657131
DOI:
10.1016/j.str.2018.03.010

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