Characterization of Campylobacter upsaliensis fur and its localization in a highly conserved region of the Campylobacter genome

Despite increasing recognition of the importance of Campylobacter upsaliensis in human disease little is known about either the virulence properties or genetics of this enteric pathogen. The complete coding sequence of a C. upsaliensis gene has yet to be published. We have cloned and sequenced the complete iron-uptake regulatory (fur) gene from the type strain of this species. The C. upsaliensis fur homolog was isolated from a genomic library of C. upsaliensis ATCC 43954 constructed in phage lambdaGEM-11. The open reading frame identified encodes a polypeptide consisting of 156 amino acids. The 5'-flanking region of the C. upsaliensis fur gene contains 3 putative Fur-binding sequences and two catabolite activator-binding sequences indicating the potential for autogenous and cAMP-mediated regulation, respectively. Primer extension analysis identified a single transcription start site 262 nt upstream from the AUG initiation codon. Sequence analysis indicates that the Fur protein of C. upsaliensis is highly homologous (87% amino acid identity) to Campylobacter jejuni Fur. Furthermore, the arrangement of the lysS and glyA genes downstream of fur is precisely conserved in both C. upsaliensis ATCC 43954 and C. jejuni TGH9011. Using the polymerase chain reaction close linkage of fur with lysS and glyA was also observed among multiple isolates of C. upsaliensis, C. jejuni and C. coli suggesting a possible functional relevance for this conserved genetic arrangement in campylobacteria.