YscO of Yersinia pestis Is a Mobile Core Component of the Yop Secretion System

Abstract

The Yersinia pestis low-Ca2+ response stimulon is responsible for the temperature- and Ca2+-regulated expression and secretion of plasmid pCD1-encoded antihost proteins (V antigen and Yops). We have previously shown that lcrD, yscC, yscD,yscG, and yscR encode proteins that are essential for high-level expression and secretion of V antigen and Yops at 37°C in the absence of Ca2+. In this study, we characterized yscO of the Yop secretion (ysc) operon that contains yscN through yscU by determining the localization of its gene product and the phenotype of an in-frame deletion. The yscO mutant grew and expressed the same levels of Yops as the parent at 37°C in the presence of Ca2+. In the absence of Ca2+, the mutant grew independently of Ca2+, expressed only basal levels of V antigen and Yops, and failed to secrete these. These defects could be partially complemented by providing yscO intrans in the yscO mutant. Overexpression of YopM and V antigen in the mutant failed to restore the export of either protein, showing that the mutation had a direct effect on secretion. These results indicated that the yscO gene product is required for high-level expression and secretion of V antigen and Yops. YscO was found by immunoblot analysis in the soluble and membrane fractions of bacteria growing at 37°C irrespective of the presence of Ca2+ and in the culture medium in the absence of Ca2+. YscO is the only mobile protein identified so far in the Yersinia species that is required for secretion of V antigen and Yops.

Transcriptional slippage controls production of type III secretion apparatus components in Shigella flexneri

“…2). As previously shown for mutants deficient in T3SA assembly (Jouihri et al, 2003), the needle component MxiH was not detected in the culture medium of the spa13 mutant (data not shown), consistent with a role of YscO-SpaM-Spa13 family members in T3SA assembly (Sasakawa et al, 1993;Collazo et al, 1995;Payne and Straley, 1998). To complement the spa13 mutant, we constructed plasmids pC78 carrying spa13a and spa13b with the wild-type slippage site and pC83 carrying spa13a and spa13b with a mutated site, such that transcriptional slippage can not occur and the sequence of the protein encoded by spa13a is unchanged.…”

“…1B). Moreover, the deduced product of spa13b (112 residues) is shorter than other members of the YscO-SpaM-Spa13 family (155 residues) (Sasakawa et al, 1993;Collazo et al, 1995;Payne and Straley, 1998). These observations suggested that Spa13 might be encoded by spa13a and spa13b.…”

Type III export: new uses for an old pathway

“…Similarly, several components of the virulence-associated TTS and translocation machineries are also export substrates. YscO and YscP are members of two poorly conserved families of secretion components that are exported to an extracellular location (Payne and Straley, 1998;Stainier et al, 2000). YscX, which is essential for Yop secretion in the yersiniae, was recently demonstrated to interact with cytosolic YscY and to be exported in a TTS-dependent manner (Day and Plano, 2000).…”

Assembly of the Yersinia injectisome: the missing pieces

“…In Yersinia, besides the needle subunit YscF and the translocators at the tip of the needle (see Table 1), three proteins that are exported themselves, YscI, YscO and YscX, are essential for the final translocation of the effectors. YscI and YscO have been shown to be already required for the assembly of the needle, like related small proteins from other T3S systems (Payne and Straley, 1998;Kimbrough and Miller, 2000). YscI resembles MxiI (Shigella) and PrgJ (Salmonella) that have been assigned to form a rod structure extending the hollow needle at the centre of the basal body (Sukhan et al, 2003;Marlovits et al, 2004;Sal-Man et al, 2012).…”