Characterization of a ferric uptake regulator (fur) gene from Xanthomonas campestris pv. phaseoli with unusual primary structure, genome organization, and expression patterns

A 1.5 kb DNA fragment from Xanthomonas campestris pv. phaseoli containing f ur was characterized, fur is a single copy gene that is transcribed as a mo nocistronic mRNA. The predicted amino acid sequence of Xp Fur showed extens ive identity to other Fur proteins. However, Xp Fur has many distinct featu res, particularly a lack of cysteine residues in the conserved metal-bindin g motifs and unusual modifications in the carboxy-terminus region. The nucl eotide sequences of fur genes from four other Xanthomonas spp. were determi ned. Deduced amino acid sequences all showed the distinct features of Xp Fu r. Functionally, Xp Fur partially repressed a Fur-regulated promoter in E c oli. Expression analysis of fur showed increased fur mRNA levels in respons e to a low iron growth condition. The fur transcription start site was iden tified by primer extension. (C) 1999 Elsevier Science B.V. All rights reser ved.