YscP, a Yersinia protein required for Yop secretion that is surface exposed, and released in low Ca²⁺

Abstract

The Yersinia Ysc apparatus is made of more than 20 proteins, 11 of which have homologues in many type III systems. Here, we characterize YscP from Yersinia enterocolitica. This 515‐residue protein has a high proline content, a large tandem repetition and a slow migration in SDS–PAGE. Unlike the products of neighbouring genes, it has a counterpart only in Pseudomonas aeruginosa and it varies even between Yersinia Ysc machineries. An yscPΔ97−465 mutant was unable to secrete any Yop, even under conditions overcoming feedback inhibition of Yop synthesis. Interestingly, a cloned yscPΔ57−324 from Yersinia pestis introduced in the yscPΔ97−465 mutant can sustain a significant Yop secretion and thus partially complemented the mutation. This explains the leaky phenotype observed with the yscP mutant of Y. pestis. In accordance with this secretion deficiency, YscP is required for the delivery of Yop effectors into macrophages. Mechanical shearing, immunolabelling and electron microscopy experiments showed that YscP is exposed at the bacterial surface when bacteria are incubated at 37°C in the presence of Ca2+ and thus do not secrete Yops. At 37°C, when Ca2+ ions are chelated, YscP is released like a Yop protein. We conclude that YscP is a part of the Ysc injectisome which is localized at the bacterial surface and is destabilized by Ca2+ chelation.

YscP and YscU Regulate Substrate Specificity of theYersiniaType III Secretion System

“…Moreover, we could also confirm the findings of others that the yscP mutant secreted much lower levels of Yops than the wild-type strain (Fig. 1B) (35,46).…”

“…In this work, we have confirmed and extended previous findings regarding the role of YscP in the TTSS by Yersinia (35,46) and shown that yscP-null mutants were severely affected in their ability to secrete Yop effector proteins. In contrast, the YscF protein was secreted in elevated amounts.…”

Shigella Spa32 Is an Essential Secretory Protein for Functional Type III Secretion Machinery and Uniformity of Its Needle Length

“…The latter two proteins are slightly larger (FliK, 42 kDa; YscP, 50 kDa) than Spa32 (32 kDa), and indeed, there are many gaps between the homologous amino acid regions of FliK (as well as YscP) and Spa32. However, the placements of spa32, invJ, fliK, and yscP in the respective operons were all similar, and each of the gene products was secreted (6,32,36,40,42; this study). Furthermore, the production of each protein was required for a functional type III secretion system (Spa32, InvJ, and YscP) (7, 36, 42; this study) or flagellar export system (FliK) (20,33,48).…”

Evolutionary Dynamics of the Yersinia enterocolitica Complex

“…Deletion mutants showed that abolishing the complete gene leads to a loss of secretion of Yops, and a functional protein is necessary for the delivery of the effectors into target cells (Stainier, et al, 2000). It was noted as well that it shows more variability than any other protein in the T3SS between Y. pseudotuberculosis, Y. pestis, and Y. enterocolitica (Stainier, et al, 2000). YscP from Y. enterocolitica has additional 60 amino acids that appear to be part of a repeat compared to Y. pseudotuberculosis and Y. pestis.…”