A low-Ca2+ response (LCR) secretion (ysc) locus lies within the lcrB region of the LCR plasmid in Yersinia pestis

Abstract

The causative agent of plague, Yersinia pestis, contains a 75-kb plasmid, pCD1, which carries a virulencerelated stimulon called the low-Ca2+ response stimulon (LCRS). LCRS operons are regulated by the environmental signals of temperature and Ca2+. This study characterized a portion of the lkrB region of pCD1, known to contain at least one gene necessary for the regulation of LCRS operons by Ca2+. Ca2" or nucleotides (11,35,78). These genes, which belong to the LCR stimulon (LCRS), encode secreted factors such as V antigen (12, 79) and a set of about 10 virulence proteins called Yops (9,58,76,77,79). Proteins regulating the expression and secretion of V antigen and Yops are encoded within a ca. 25-kb region of the LCR plasmid termed the Ca2' dependence region (9,13,24,57,78,83).One manifestation of the LCR is the requirement for millimolar calcium or 10 to 20 mM nucleotides, such as ATP, for growth above 34°C (28,84,85). Although growth occurs independently of Ca2+ or ATP at 26°C, a shift in incubation temperature to 37°C in the absence of Ca2+ or ATP results in a cessation of growth within a few generations (28,84). This phenomenon is termed growth restriction. Paradoxically, restriction is concurrent with maximal induction of LCRS operons and secretion of LCRS-encoded proteins.V antigen is a soluble protein encoded by the kcrV gene of the lcrGVH-yopBD operon (5,52,59). Although a specific antihost function has not been assigned to V antigen, it is a protective antigen and is believed to be required for full virulence (10,36,73 (65, 66), and sequestration of thrombin (38, 64). V antigen and Yops lack cleavable N-terminal signal sequences and are secreted by an LCRS-encoded mechanism (45). N-terminal sequences have been implicated in directing transport from the cell (43).Previously, two loci within the Ca2" dependence region have been shown to affect both LCRS operon transcription and secretion. LcrD of the lcrDR operon is necessary for maximal induction of LCRS operons and secretion of LCRS-encoded virulence proteins (24,54,55). LcrD has homology to several proteins associated with flagellar biogenesis, invasion of epithelial cells, and plant pathogenesis in taxonomically divergent bacteria (54,78). The LcrD homolog is thought to be a component of a novel secretion system involved in each of these diverse processes.The 13-cistronysc locus is also necessary for the secretion of the V antigen and Yops (27,44). Polar insertion mutants of this region are defective in LCR-specific secretion and show altered regulation of LCRS operon transcription (24,27,44). However, the dominant effects on regulation are the opposite between Y pestis and the enteropathogenic yersiniae, with constitutive downregulation being seen in the former and constitutive induction being seen in the latter (24,27,44). This could arise from different extents of polarity in the respective ysc loci, and sorting out these differences will require analysis of nonpolar mutants in the various ysc genes.Early studies involving the mutagenesis of the Y...

Functional conservation of the secretion and translocation machinery for virulence proteins of yersiniae, salmonellae and shigellae.

“…These related proteins play an essential role in surface presentation of the virulence determinants and are likely to serve a similar function in the different species. Some of the gene products of the yscA-M operon of Yersinia show high homology to proteins involved in secretion of Ipas and Sips (Rosqvist et al, 1990;Rimpilainen et al, 1992;Allaoui et al, 1993;Plano and Straley, 1993;Fields et al, 1994;Kaniga et al, 1994). The yscN-U gene cluster encodes proteins which show striking homology with the inv/spa gene products of S.typhimurium and the Spa proteins of Sflexneri (Venkatesan et al, 1992;Groisman and Ochman, 1993;Sasakawa et al, 1993;Allaoui et al, 1994;Bergman et al, 1994;Eichelberg et al, 1994;Fields et al, 1994;Woestyn et al, 1994).…”

“…Three different operons, IcrDR, yscA-M and yscN-U, are involved in Yop secretion (Rosqvist et al, 1990;Rimpilainen et al, 1992;Plano and Straley, 1993;Allaoui et al, 1994;Bergman et al, 1994;Fields et al, 1994;Woestyn et al, 1994). LcrD of Yersinia is a 75 kDa cytoplasmic membrane protein that shows high homology to MxiA of Sflexneri and InvA of S.typhimurium (Plano et al, 1991;Andrews and Maurelli, 1992;Galan et al, 1992).…”

Hrp pilus: An hrp -dependent bacterial surface appendage produced by Pseudomonas syringae pv. tomato DC3000

“…16), share sequence similarities with ysc͞lcr genes of Yersinia spp. (17)(18)(19), mxi-spa genes of Shigella (20), and inv genes of Salmonella (21,22), all of which function in secretion of proteins required for pathogenesis. The protein products of hrc genes and related counterparts in animal pathogenic bacteria are predicted to be components of a novel protein secretion pathway, the so-called type III secretion pathway, in Gram-negative bacteria.…”

The type III secretion injectisome, a complex nanomachine for intracellular ‘toxin’ delivery

“…Among the nine conserved proteins, eight are shared with the flagellum (Fields et al, 1994;Woestyn et al, 1994;Van Gijsegem et al, 1995), suggesting a common evolutionary origin, which is also evidenced by the similarity of their basal body structure (Kubori et al, 1998). Injectisomes have evolved into seven different families (Gophna et al, 2003;Pallen et al, 2005;Troisfontaines and Cornelis, 2005).…”

“…Among the eight proteins that are highly conserved between flagella and injectisomes, five (YscR, S, T, U, V) are TM ahelical proteins (Plano and Straley, 1993;Allaoui et al, 1994;Fields et al, 1994). They are thought to form the translocation channel(s) embedded in a patch of IM enclosed within the IM-ring but this view awaits biochemical confirmation.…”