THE YERSINIABACTIN BIOSYNTHETIC GENE-CLUSTER OF YERSINIA-ENTEROCOLITICA - ORGANIZATION AND SIDEROPHORE-DEPENDENT REGULATION

The ability to synthesize and uptake the Yersinia siderophore yersinia bactin is a hallmark of the highly pathogenic, mouse-lethal species Ye rsinia pestis, Y. pseudotuberculosis, and Y. enterocolitica 1B. We hav e identified four genes, hpl, irp3, irp4, and irp5, on a 13-kb chromos omal DNA fragment of Y. enterocolitica O8, WA-314, These gents constit ute the yersiniabactin biosynthetic gene cluster together with the pre viously defined irp2. The irp1 gene consists of 9,486 hp capable of en coding a 3,161-amino-acid high-molecular-weight protein I (HMWP1) poly peptide with a predicted mass of 384.6 kDa. The first 3,000 bp of irp1 show similarity to the corresponding regions of the polyketide syntha se genes of Bacillus subtilis and Streptomyces antibioticus. The remai ning part of irp1 is most similar to irp2, encoding HMWP2, which might be the reason for immunological cross-reactivity of the two polypepti des. irp4 was found to have 41.7% similarity to thioesterase-like prot ein of the anguibactin biosynthetic genes of Vibrio anguillarum, Irp5 shows 41% similarity to EntE, the 2,3-dihydroxy-benzoic acid-activatin g enzyme utilized in enterobactin synthesis of Escherichia coli, Hl,pl and Irp5 are nearly identical to YbtT and YbtE, recently identified i n Y. pestis. irp3 has no similarity to any known gene. Inactivation of either irp1 or irp2 abrogates yersiniabactin synthesis, Mutations in irp1 or fyuA (encoding yersiniabactin/pesticin receptor) result in dow nregulation of irp2 that can be upregulated by the addition of yersini abactin. A Fyu-green fluorescent protein translational fusion was down regulated in an irp1 mutant, Upregulation was achieved by addition of yersiniabactin but not desferal, pesticin, or pyochelin, which indicat es high specificity of the FyuA receptor and autoregulation of genes i nvolved in synthesis and uptake of yersiniabactin.