This family contains the bacterial type III secretion protein YscO, which is approximately 150 residues long. YscO has been shown to be required for high-level expression and secretion of the anti-host proteins V antigen and Yops in Yersinia pestis [1].

1: YscO of Yersinia pestis is a mobile core component of the Yop secretion system. Payne PL, Straley SC; J Bacteriol 1998;180:3882-3890. PMID:9683485