[Nucleotide correspondence between protein-coding sequences of Helicobacter pylori 26695 and J99 strains]

Comparison of open-reading frames (ORFs) H. pylori 26695 and J99 strains has been revealed prevalence of nucleotide replacements as transitions (more than 3%) above transversions (less than 1%). Prevalence of nucleotide transitions is caused by high speed of C : G to T : A transitions in a coding strand of DNA (3.5-5.3%) and not coding strand (2.9-3.9%). The correspondence rate of transversion (A --> C, A --> T, C --> A, C --> G, G --> C, G --> T, T --> A and T --> G) did not exceed 0.84%. The highest correspondence frequency between C and T was detected in ACGT-ATGT (28.3%) - the site of methylation by active methyltransferase M.Hpy99XI in H. pylori 26695 and J99. Thus one can speculate that predominant transition taking place in H. pylori is mutation of C into T, which is realized through cytosine methylation-deamination mechanism.