opB

opB is a gene symbol used in several Gram-negative bacteria to designate an outer membrane protein B, often an outer membrane porin. The precise identity and role of opB-encoded proteins vary by species and context, but they are generally components of the bacterial outer membrane involved in the transport of small molecules.

Protein features: opB-encoded proteins are typically exported across the inner membrane via the Sec pathway, possessing an N-terminal signal sequence that is cleaved after export. They fold into beta-barrel structures that span the outer membrane and form channels for hydrophilic solutes. Substrate range and channel properties are species-specific and determined by loop regions.

Biological role: By forming porin channels, opB proteins influence nutrient uptake, waste removal, and interactions with the environment. In some bacteria their porin properties affect susceptibility to antibiotics and other antimicrobial compounds; in others they may contribute to virulence, adhesion, or biofilm formation, though these roles are not universal.

Genomic context and regulation: opB genes are often located within operons or gene clusters encoding outer membrane proteins or porins; expression can be regulated by environmental factors such as osmolarity, temperature, and growth phase, and may respond to stress signals through two-component regulatory systems.

See also: outer membrane protein, porin. The designation opB is organism- and context-dependent, and should not be assumed to have a single universal function across bacteria.