This Autotransporter-associated beta strand repeat model represents a core 32-residue region of a class of bacterial protein repeat found in one to 30 copies per protein. Most proteins with a copy of this repeat have domains associated with membrane autotransporters (Pfam:PF03797). The repeats occur with a periodicity of 60 to 100 residues. A pattern of sequence conservation is that every second residue is well-conserved across most of the domain. These repeats as likely to have a beta-helical structure. This repeat plays a role in the efficient transport of autotransporter virulence factors to the bacterial surface during growth and infection. The repeat is always associated with the passenger domain of the autotransporter. For these reasons it has been coined the Passenger-associated Transport Repeat (PATR) [1]. The mechanism by which the PATR motif promotes transport is uncertain but it is likely that the conserved glycines (see HMM Logo) are required for flexibility of folding and that this folding drives secretion [1]. Autotransporters that contain PATR(s) associate with distinct virulence traits such as subtilisin (S8) type protease domains and polymorphic outer-membrane protein repeats, whilst SPATE (S6) type protease and lipase-like autotransporters do not tend to contain PATR motifs [1].

1: The passenger-associated transport repeat promotes virulence factor secretion efficiency and delineates a distinct autotransporter subtype. Doyle MT, Tran EN, Morona R; Mol Microbiol. 2015; [Epub ahead of print] PMID:25869731