Date Published: January 01, 2018
Publisher: International Union of Crystallography
Author(s): Huanyu Li, Weijiao Zhang, Changjiang Dong.
The crystal structure of the major outer membrane protein U (OmpU) from Vibrio cholerae has been determined, which exhibits distinct structural features from other structurally characterized porins and provides the structural basis for the bacterial invasion and phage recognition.
Vibrio cholerae is the causal organism of the disease cholera, which is a severe public health problem. In 2012, it caused 7816 deaths (World Health Organization, 2012 ▸). Serogroups O1 and O139 are responsible for epidemics. In the small intestine, the major cholera toxin, along with other virulence factors of V. cholerae, are synthesized under genetic modulation by the toxR regulon. There are two other genes, ompU and ompT, which encode two major outer membrane proteins (OMPs) that are also regulated by the transcriptional activator ToxR (Miller & Mekalanos, 1988 ▸; Provenzano & Klose, 2000 ▸).
OmpU has long been proposed as a potential virulence factor involved in pathogen–host interactions during infection, being capable of making physical contact with and adhering to host cells, as well as triggering subsequent invasion by the pathogen. Given its abundance in the outer membrane of V. cholerae and its implications in adhesion and invasion, experimentally produced ΔompU strains showed a reduced ability to express a virulence factor and colonize the intestine (Provenzano & Klose, 2000 ▸). Moreover, OmpU porins are increasingly being recognized as one of the crucial determinants of Vibrio pathogen–host interactions (Duperthuy et al., 2011 ▸; Liu et al., 2015 ▸; Sperandio et al., 1995 ▸). Here, we have reported the first crystal structure of the OmpU trimer and have shown a number of defining features that can differentiate OmpU from other structurally related porins. OmpU possesses a unique N-terminal coil consisting of Gly32–Ser42 that extends into the pore at the periplasmic side and forms a second gate with the constriction loop L3. In addition, the L4 loop at the extracellular side exhibits a signature ‘pole’ structure and protrudes further into the extracellular space.
The following reference is cited in the Supporting Information for this article: Robert & Gouet (2014 ▸).