OmpA-like transmembrane domain is an evolutionarily conserved domain

Protein domain

A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...

 of outer membrane

Outer membrane

The bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's...

 proteins. This domain consists of an eight-stranded beta barrel

Beta barrel

A beta barrel is a large beta-sheet that twists and coils to form a closed structure in which the first strand is hydrogen bonded to the last.Beta-strands in beta-barrels are typically arranged in an antiparallel fashion...

. OmpA is the predominant cell surface antigen

Antigen

An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...

 in enterobacteria found in about 100,000 copies per cell. The expression of OmpA is tightly regulated by a variety of mechanisms. One mechanism by which OmpA expression is regulated in Vibrio

Vibrio

Vibrio is a genus of Gram-negative bacteria possessing a curved rod shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in saltwater, Vibrio are facultative anaerobes that test positive for oxidase and do not form...

 species is by an antisense non-coding RNA

Non-coding RNA

A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...

 called VrrA

Vibrio regulatory RNA of OmpA

VrrA is a non-coding RNA that is conserved across all Vibrio species of bacteria and acts as a repressor for the synthesis of the outer membrane protein OmpA...

.