CagS is a family of proteins from the pathogenicity island of Helicobacter pylori. The gene lies just downstream of the cluster whose protein-products resemble those of the Vibrio proteins that form the structural core of T4SS. The exact function of CagS is not known [1].

1: The crystal structure of CagS from the Helicobacter pylori pathogenicity island. Cendron L, Tasca E, Seraglio T, Seydel A, Angelini A, Battistutta R, Montecucco C, Zanotti G; Proteins. 2007;69:440-443. PMID:17623849