Pertactin-like passenger domains (virulence factors) of autotransporter proteins of the type V secretion system. Autotransporters are proteins used by Gram-negative bacteria to transport proteins across their outer membranes. The C-terminal (beta) domain of autotransporters forms a pore in the outer membrane through which the N-terminal passenger domain is transported. Following transport, the passenger domain is generally cleaved by an outer membrane protease with the passenger domain either remaining in contact with the surface via a noncovalent interaction with the beta domain or cleaved to release a soluble protein. These proteins are highly diverse and perform a variety of functions that promote virulence, including catalyzing proteolysis, serving as an adhesin, mediating actin-promoted motility, or serving as a cytotoxin. Proteins in this family share similarity in the C-terminal region of the passenger domain as seen in the pertactin structure P.69, a Bordetella pertussis agglutinogen responsible for human pertussis. The P.69 protein consists of a 16-stranded parallel beta-helix with a V-shaped cross-section, and is one of the largest beta-helix known to date.
Jiyao W et al.(2023). "The conserved domain database in 2023.",