Yersiniabactin/pesticin receptor: a component of an iron uptake system of highly pathogenic Yersinia.
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Biomedical subjects
A Rakin
Publications and source records attributed to A Rakin.
The pesticin receptor of Yersinia enterocolitica: a novel virulence factor with dual function.
The iron-repressible outer membrane protein FyuA of Yersinia enterocolitica operates as a receptor with dual function: (i) as a receptor for the Y. pestis bacteriocin pesticin, and (ii) as a receptor for yersiniabactin, a siderophore that is produced by mouse-virulent Y. enterocolitica strains of biogroup IB. Cloning of the FyuA-encoding gene was achieved by mobilization of a genomic cosmid library of the pesticin-sensitive and mouse-virulent Y. enterocolitica O:8 strain WA into the pesticin-resistant WA fyuA mutant and subsequent in vivo selection of transconjugants for the ability to survive and multiply in mice (phenotype mouse virulence). The reisolated transconjugants which survived in mice for 3 d harboured a unique cosmid and phenotypically were pesticin sensitive. From this cosmid a 2650 bp SalI-PstI fragment conferring pesticin sensitivity was subcloned. Sequencing of this DNA fragment revealed a single open reading frame of 2022 bp, which encodes a deduced polypeptide of 673 amino acids with a predicted molecular mass of 73,677 Da. Cleavage of a putative signal sequence composed of 22 amino acids should lead to a mature protein of 651 amino acids with a molecular mass of 71,368 Da. The open reading frame is preceded by a sequence which shares homology with the postulated consensus Fur iron-repressor protein-binding site. FyuA shows homology to other iron-regulated TonB-dependent outer membrane proteins with receptor functions (e.g. BtuB, CirA, FepA, IutA, FhuA, FoxA, FcuA). On the basis of multiple alignment of amino acid sequences of FyuA and other TonB-dependent receptors, a phylogenetic tree was constructed, demonstrating that FyuA probably belongs to the citrate subfamily or represents a new subfamily of TonB-dependent receptors. Moreover, by complementation of the WA fyuA mutant by the cloned fyuA gene, yersiniabactin uptake and mouse virulence were restored. These studies demonstrate that the cloned pesticin/yersiniabactin receptor FyuA of Y. enterocolitica has the typical features of iron-regulated TonB-dependent outer membrane receptors for siderophores and bacteriocins and is required for mouse virulence.
Amino Acid Sequence↗
Virulence of Yersinia enterocolitica is closely associated with siderophore production, expression of an iron-repressible outer membrane polypeptide of 65,000 Da and pesticin sensitivity.
Iron-repressible outer membrane proteins (Irp) and siderophore production of Yersinia enterocolitica, serotype 08, were subjected to analysis. Here four Irps of apparent molecular weights of 62,000, 65,000, 74,000 and 75,000 could be identified which were expressed constitutively by a fur mutant. Production of a novel catechol-containing siderophore (denoted yersiniabactin) was detected by siderophore-indicator agar (chrome azurol S) and feeding experiments. Growth support by yersiniabactin under iron-restricted conditions was TonB- and Irp65-dependent and correlated with pesticin-sensitivity of Yersinia enterocolitica and Escherichia coli O. From these results we conclude that Irp65 of Y. enterocolitica functions as yersiniabactin receptor (FyuA) and as pesticin receptor. By immunoblotting using rabbit antibodies against Irp65 and chrome azurol S-agar, we were able to demonstrate that all tested mouse-lethal Y. enterocolitica and Yersinia pseudotuberculosis strains of different serotypes express siderophores and Irp65. Moreover, the anti-Irp65 rabbit serum did not cross-react with the known iron-repressible high-molecular-weight proteins (HMWPs). Evidently, the mouse lethality trait in enteropathogenic Yersinia spp. is closely associated with a novel iron-uptake system, comprising the production of a siderophore and a siderophore receptor of apparent molecular mass 65,000 Da.
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The established Yersinia pestis biovars are characterized by typical patterns of I-CeuI restriction fragment length polymorphism.
The genomes of three main biovars of Yersinia pestis were subjected to restriction fragment length polymorphism analysis using I-CeuI endonuclease. I-CeuI which is encoded by a mobile intron in Chlamydomonas engamenans recognizes a 25-bp site in the ribosomal RNA rrl gene and cuts DNA of most representatives of Enterobacteriaceae into seven fragments corresponding to the presence of seven rrn-operons. Glycerol-positive Y. pestis strains (biovars antiqua and mediaevalis) contain seven ribosomal operons which can be recognized by I-CeuI endonuclease. However, glycerol-negative strains of Y. pestis biovar orientalis expose only six restriction sites for I-CeuI. The restriction fragment length polymorphism patterns obtained with I-CeuI make it possible to distinguish between three biovars of Y. pestis. Use of another rare cutting restriction enzyme, Bln/I, permits differentiation between pigment-adsorbing and avirulent non-pigment-adsorbing Y. pestis. Still, due to homologous recombination between the two copies of IS 100 insertion sequence bracketing the pgm-locus, the mechanism of deletions in the pgm-locus seems to be confined only to strains of biovars antiqua and mediaevalis, and can be different in Y. pestis strains of biovar orientalis. The I-CeuI restriction patterns of two Yersinia strains isolated within a ten-year period in the port of St. Petersburg and originally identified as Y. pseudotuberculosis 01 turned out to be related to typical representatives of Y. pestis biovar antiqua. These strains could be exported from the same source or circulate among Rattus norvegicus population of the port as non-pigment-adsorbing avirulent immunogenic clone.
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