The POTRA domain (for polypeptide-transport-associated domain) is found towards the N-terminus of ShlB family proteins (Pfam:PF03865). ShlB is important in the secretion and activation of the haemolysin ShlA. It has been postulated that the POTRA domain has a chaperone-like function over ShlA; it may fold back into the C-terminal beta-barrel channel [1].

1: POTRA: a conserved domain in the FtsQ family and a class of beta-barrel outer membrane proteins. Sanchez-Pulido L, Devos D, Genevrois S, Vicente M, Valencia A; Trends Biochem Sci 2003;28:523-526. PMID:14559180