yscC

YscC is the outer membrane secretin component of the Yersinia type III secretion system (T3SS). It is also referred to as SctC in the broader secretion system nomenclature. YscC is encoded on the virulence plasmid pYV in pathogenic Yersinia species, including Yersinia pestis, Y. enterocolitica, and Y. pseudotuberculosis.

Functionally, YscC forms a multimeric pore in the outer membrane that constitutes the outer membrane ring of the injectisome. This secretin channel, together with inner membrane components such as YscD and YscJ, completes the basal body that spans the bacterial envelopes. The secretin pore provides a conduit through which effector proteins, such as the Yops, are translocated from the bacterial cytoplasm into host cells. YscC interacts with other T3SS components to enable substrate delivery and is essential for productive secretion.

Structurally, YscC belongs to the secretin family and assembles into a cylindrical, multimeric complex in the outer membrane. The assembled secretin forms a pore that often incorporates a periplasmic vestibule guiding substrates toward the channel. Secretin assembly typically involves auxiliary factors that assist outer membrane targeting and integration; in Yersinia, YscC coordinates with the rest of the apparatus to form a functional injectisome.

Regulation and role in virulence: expression of YscC and the Ysc-Yop T3SS is controlled by environmental cues such as temperature and calcium concentration and is driven by the transcriptional activator LcrF/VirF. Mutation or deletion of yscC attenuates virulence by disrupting effector translocation into host cells.

See also: Type III secretion system; Yop proteins; YscD; YscJ; YscN.