Divergence of genetic sequences for the vacuolating cytotoxin among Helicobacter pylori strains.
Divergence of genetic sequences for the vacuolating cytotoxin among Helicobacter pylori strains.
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发表时间：
1994-04
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通讯作者：
T. Cover;M. Tummuru;P. Cao;S. Thompson;M. Blaser
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作者：
T. Cover;M. Tummuru;P. Cao;S. Thompson;M. Blaser
大约50%的幽门螺杆菌分离株在体外产生细胞毒素，诱导真核细胞空泡化。筛选H. pylori 60190染色体片段允许鉴定编码空泡细胞毒素的3864碱基对（bp）开放阅读框（vacA）和与大肠杆菌半胱氨酰-tRNA合成酶同源的>或= 567 bp上游基因。序列数据表明，33个氨基酸的前导序列和C-末端肽从139-kDa的原毒素切割，产生成熟的87-kDa的细胞毒素。vacA基因产物含有C-末端基序，其存在于经历C-末端切割的几种其他细菌蛋白质中，包括流感嗜血杆菌和淋病奈瑟菌的伊加蛋白酶。等基因H.具有vacA基因插入突变的pylori突变体缺乏空泡化细胞毒素活性，并且不能产生87-kDa蛋白。天然存在的tox-H的Southern分析。pylori菌株的vacA探针表明存在杂交条带，但Southern分析和聚合酶链反应研究都表明tox-菌株的vacA序列不同于tox+菌株。tox-菌株87-203的聚合酶链反应扩增的vacA的1541-bp区域的序列分析表明与tox+菌株60190的相应区域具有64.8%的氨基酸同一性。因此，vacA基因的序列差异可以解释某些H.幽门螺杆菌分离株。
Approximately 50% of Helicobacter pylori isolates produce a cytotoxin in vitro that induces vacuolation of eukaryotic cells. Screening a lambda ZapII library of H. pylori 60190 chromosomal fragments permitted the identification of a 3864-base pair (bp) open reading frame (vacA) that encoded the vacuolating cytotoxin, and a > or = 567-bp upstream gene that was homologous to Escherichia coli cysteinyl-tRNA synthetase. The sequence data suggest that a 33-amino-acid leader sequence and a C-terminal peptide are cleaved from a 139-kDa protoxin to yield the mature 87-kDa cytotoxin. The vacA gene product contains a C-terminal motif that is present in several other bacterial proteins that undergo C-terminal cleavage, including IgA proteases of Haemophilus influenzae and Neisseria gonorrhoeae. Isogenic H. pylori mutants with insertional mutation of the vacA gene lacked vacuolating cytotoxin activity and failed to produce the 87-kDa protein. Southern analysis of naturally occurring tox-H. pylori strains with vacA probes indicated the presence of hybridizing bands, but both Southern analysis and polymerase chain reaction studies suggested that the vacA sequences of tox- strains differed from those of tox+ strains. Sequence analysis of a 1541-bp region of polymerase chain reaction-amplified vacA from tox- strain 87-203 indicated 64.8% amino acid identity with the corresponding region from tox+ strain 60190. Thus, sequence divergence in vacA genes may explain the lack of functionally active cytotoxin production by some H. pylori isolates.