An ABC Transporter System of Yersinia pestis Allows Utilization of Chelated Iron by Escherichia coli SAB11

Abstract

The acquisition of iron is an essential component in the pathogenesis of Yersinia pestis , the agent of bubonic and pneumonic plague. A cosmid library derived from the genomic DNA of Y. pestis KIM6+ was used for transduction of an Escherichia coli mutant (SAB11) defective in the biosynthesis of the siderophore enterobactin. Recombinant plasmids which had a common 13-kb Bam HI fragment were isolated from SAB11 transductants in which growth but not enterobactin synthesis was restored on media containing the iron chelator EDDA [ethylenediamine-di( o -hydroxyphenyl acetic acid)]. Subcloning and transposon mutagenesis revealed a 5.6-kb region, designated yfe , essential for SAB11 growth stimulation. In vitro transcription-translation analysis identified polypeptides of 18, 29.5, 32, and 33 kDa encoded by the yfe locus. Sequence analysis shows this locus to be comprised of five genes in two separate operons which have potential Fur-binding sequences in both promoters. A putative polycistronic operon, yfeABCD , is Fur regulated and responds to iron and manganese. A functional Fur protein is required for the observed manganese repression of this operon. This operon encodes polypeptides which have strong similarity to the ATP-binding cassette (ABC) family of transporters and include a periplasmic binding protein (YfeA), an ATP-binding protein (YfeB), and two integral membrane proteins (YfeC and -D), which likely function in the acquisition of inorganic iron and possibly other ions. The ∼21-kDa protein encoded by the separately transcribed yfeE gene may be located in the cell envelope, since a yfeE ::Tn phoA fusion is PhoA + . Mutations in this gene abrogate growth of SAB11 on iron-chelated media.