Outer membrane protein, beta-barrel <p>This entry represents a transmembrane beta (8,10)-barrel found in outer membrane proteins such as OmpA, OmpX and NspA, and in the outer membrane enzyme PagP [<cite idref="PUB00035651"/>]. OmpA is multifunctional, being required for the action of colicins K and L, and for the stabilisation of mating aggregates in conjugation; it also serves as a receptor for a number of T-even like phages, and can act as a porin with low permeability that allows slow penetration of small solutes [<cite idref="PUB00035653"/>]. OmpX is a cation-selective channel that is regulated by osmolarity and by MarA expression [<cite idref="PUB00035652"/>]. NspA (Neisseria surface protein A) is an iron-activated membrane protein of unknown function [<cite idref="PUB00035654"/>]. The outer membrane enzyme PagP catalyses palmitate transfer from a phospholipid to a glucosamine unit of lipid A [<cite idref="PUB00035655"/>].</p>