has role protective antigen role protective antigen Yersinia pestis protein YopD from Y. pestis CO92 Allen Xiang protein Protegen ID: 49; NCBI Gene GI: 1172673; NCBI Protein GI: 16082716; NCBI Protein Accession: NP_395162; NCBITaxon: 214092 Oliver He The type III secretion apparatus encoded on the low-calcium response (LCR) virulence plasmid, pCD1 in strain KIM5, of Y. pestis is a conserved virulence mechanism that is absolutely required for virulence of Y. pestis. YscF is a surface localized protein required both to secrete Yops and to translocate toxins into eukaryotic cells. YscF polymerization is possibly required for a YscF needle to puncture eukaryotic cell membranes. It is also likely that YscF and its homologs function to provide a base that a translocon complex is built upon, or that YscF builds a conduit from the bacterium to the eukaryotic membrane - this suggestion seems more likely given that other proteins such as YopB, YopD, and LcrV are also required for translocation into eukaryotic cells. YscF is thought to be a surface-expressed protein in Y. pestis and is required for virulence. YscF has been found to function as a protective antigen against experimental plague infection [PubMed: 15978133].