Two distinct cytotoxic activities of subtilase cytotoxin produced by shiga-toxigenic Escherichia coli
Two distinct cytotoxic activities of subtilase cytotoxin produced by shiga-toxigenic Escherichia coli
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DOI：
10.1128/iai.01336-06
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发表时间：
2007-01-01
影响因子：
3.1
通讯作者：
Noda, Masatoshi
中科院分区：
文献类型：
--
作者：
Morinaga, Naoko;Yahiro, Kinnosuke;Noda, Masatoshi
枯草杆菌酶细胞毒素（Subtilase cytotoxin，SubAB）是最近发现的一种由志贺菌大肠杆菌产生的AB 5亚单位毒素。A亚基被认为是枯草杆菌酶样丝氨酸蛋白酶，而B亚基与细胞表面的毒素受体结合。我们从一个临床分离株中克隆了这些基因;毒素是以His标记的蛋白质形式产生的。除了报告的48小时后在ng/ml水平诱导的细胞毒性外，8小时后浓度大于1 μ g/ml的SubAB诱导空泡化。B亚基而非A亚基可诱导腺苷酸化，且腺苷酸化依赖于V型ATP酶。低浓度SubAB的细胞毒性与蛋白质合成的抑制有关; 50%抑制剂量与1 ng/ml相似。A亚基含有丝氨酸272，被认为是枯草杆菌酶样丝氨酸蛋白酶催化三联体的一部分，加上B亚基是体内和体外活性所必需的。SubAB不裂解偶氮酪蛋白、牛血清白蛋白、卵清蛋白或合成肽。这些数据表明SubAB是一种独特的AB毒素：首先，B亚基单独可诱导空泡化;其次，含丝氨酸272的A亚基加上B亚基在体内和体外均抑制蛋白质合成;第三，A亚基蛋白水解活性可能具有严格的底物特异性范围。
Subtilase cytotoxin (SubAB) is a recently identified AB5 subunit toxin produced by Shiga-toxigenic Escherichia coli. The A subunit is thought to be a subtilase-like, serine protease, whereas the B subunit binds to the toxin receptor on the cell surface. We cloned the genes from a clinical isolate; the toxin was produced as His-tagged proteins. SubAB induced vacuolation at concentrations greater than 1 mu g/ml after 8 h, in addition to the reported cytotoxicity induced at a ng/ml level after 48 h. Vacuolation was induced with the B, but not the A, subunit and was dependent on V-type ATPase. The cytotoxicity of SubAB at low concentrations was associated with the inhibition of protein synthesis; the 50% inhibitory dose was similar to 1 ng/ml. The A subunit, containing serine 272, which is thought to be a part of the catalytic triad of a subtilase-like serine protease, plus the B subunit was necessary for this activity, both in vivo and in vitro. SubAB did not cleave azocasein, bovine serum albumin, ovalbumin, or synthetic peptides. These data suggest that SubAB is a unique AB toxin: first, the B subunit alone can induce vacuolation; second, the A subunit containing serine 272 plus the B subunit inhibited protein synthesis, both in vivo and in vitro; and third, the A subunit proteolytic activity may have a strict range of substrate specificity.