大肠杆菌素D的切割对于细胞杀伤是必需的，并且需要内膜肽酶LepB。
Cleavage of colicin D is necessary for cell killing and requires the inner membrane peptidase LepB.
作者信息
de Zamaroczy M, Mora L, Lecuyer A, Géli V, Buckingham R H
机构信息
Institut de Biologie Physico-Chimique, CNRS, UPR 9073, 75005, Paris, France.
出版信息
Mol Cell. 2001 Jul;8(1):159-68. doi: 10.1016/s1097-2765(01)00276-3.
Colicin D is known to kill target cells by cleaving tRNA(Arg). A colicin D-resistant mutant was selected that was altered in the inner membrane leader peptidase, LepB. The substituted residue (Asn274Lys) is located close to the catalytic site. The mutation abolishes colicin D cleavage but not the processing of exported proteins. LepB is required for colicin D cleavage, releasing a small C-terminal fragment that retains full tRNase activity. The immunity protein was found to prevent colicin D processing and furthermore masks tRNase activity, thus protecting colicin D against LepB-mediated cleavage during export. Catalytic colicins share a consensus sequence at their putative processing site. Mutations affecting normal processing of colicin D abolish cytotoxicity without affecting the in vitro tRNase activity.
已知大肠杆菌素D通过切割tRNA（精氨酸）来杀死靶细胞。筛选出了一种对大肠杆菌素D具有抗性的突变体，该突变体在内膜前导肽酶LepB中发生了改变。取代的残基（Asn274Lys）位于靠近催化位点的位置。该突变消除了大肠杆菌素D的切割作用，但不影响输出蛋白的加工。大肠杆菌素D的切割需要LepB，释放出一个保留完整tRNase活性的小C端片段。发现免疫蛋白可阻止大肠杆菌素D的加工，并且还能掩盖tRNase活性，从而在输出过程中保护大肠杆菌素D免受LepB介导的切割。催化性大肠杆菌素在其假定的加工位点共享一个共有序列。影响大肠杆菌素D正常加工的突变消除了细胞毒性，但不影响体外tRNase活性。
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