[Sequence analysis of two different subtypes of thioredoxin gene of Helicobacter pylori].

Objective: To analyze the gene sequences of Trx1 and Trx2 of Helicobacter pylori (HP) from different gastric diseases, define the amino acid sequences and investigate the relationship with these diseases.

Methods: The HP strains were isolated from gastric mucosa of 25 patients with chronic gastritis, peptic ulcer and gastric cancer respectively and cultured on solid blood agar medium. The primers of Trx1 and Trx2 were designed according to the sequences of GenBank. The Trx1 and Trx2 were respectively amplified by PCR (polymerase chain reaction) and were sequenced by the bioinformatics method. The sequences were compared with those of the international standard HP strains.

Results: The whole sequence of Trx1 and the first 295 bp of Trx2 were successfully amplified to allow for sequence comparison by BioEdit. The Trx1 from different HP strains contained 321 bp encoding 106 amino acids. The mutation ratio was 13.4% (43/321). All amino acids contained the same active motif Cys-Gly-Pro-Cys. The homology of Trx1 amino acids from 25 strains was 97.2% (103/106). The mutation ratio for first 295 bp of Trx2 was 18.6% (55/295). All amino acids encoded by Trx2 contained one CXXC zone while the Cys-Gly-Pro-Cys motif was not found. The homology of Trx2 amino acids was 84.7% (83/98).

Conclusion: Two different subtypes of Trx from clinically isolated Hp strains have mutation sites. But the homology of encoded amino acids is relatively high because of invalid mutations. Trx1 of HP strains from different diseases all contains a redox active motif Cys-Gly-Pro-Cys while Trx2 contains only a CXXC zone. The above results will provide valuable rationales for future studies of the biological function and pathogenic mechanisms of HP Trx1 and Trx2.