Molecular characterisation of urease genes from urease-positive thermophilic campylobacters (UPTC).

This study aims to clarify the molecular characteristics of the urease gene operon from urease-positive thermophilic campylobacters (UPTC) obtained from different sources and in various countries. Sequence heterogeneity was observed for the promoter structures at the -35-like region among the 12 isolates examined. The most probable TTG start codon was suggested for the ureB and ureH genes, and for the ureA, E, F and G genes, ATG was suggested among all the isolates examined. Overlap was detected between ureA and ureB and between ureB and ureE among all the isolates examined. UPTC is the first example of an overlap between the two structural genes ureA and ureB. When the completely sequenced open reading frames (ORFs) for ureE, ureF, ureG and ureH were identified, non-coding regions between ureE and ureF, ureF and ureG, and ureG and ureH were also demonstrated. All six start codons of the six urease genes were demonstrated to be preceded by Shine-Dalgarno sequences among all the isolates examined. The Cys-His sequence corresponding to urease active sites were aligned perfectly and fully conserved among the three UPTC isolates examined. A putative and intrinsic p-independent transcriptional terminator was identified to be identical among all the isolates examined. A partial and putative ORF of about 200 bp in length showing high sequence similarity to GTP cyclohydrolase I was observed downstream of ureH.