CHARACTERIZATION OF MAMMALIAN ADP-RIBOSLYTRANSFERASES

单ADP核糖基化，一种蛋白质翻译后修饰， 其中NAD的ADP-核糖部分被转移到蛋白质， 导致某些细菌毒素的毒性（例如，霍乱 毒素、百日咳毒素）。 NAD：精氨酸ADP-核糖基转移酶克隆 来自人和兔骨骼肌以及来自小鼠淋巴瘤细胞（Yac， 1 ADP-核糖基转移酶），是糖基磷脂酰肌醇（GPI）- 锚定并具有类似的酶和物理性质。 第二 从小鼠淋巴瘤细胞中克隆了ADP-核糖基转移酶（Yac-2）， 其性质不同于先前鉴定的真核生物 转移酶 该基因的核苷酸和推导的氨基酸序列 Yac-1和Yac-2转移酶分别为58%和33%相同。 的 Yac-2蛋白是膜结合的，但与Yac-1酶不同， 是GPI锚定的 Yac-1和Yac-2酶，表示为 谷胱甘肽-S-转移酶融合蛋白在E.大肠杆菌，用于 比较它们的ADP-核糖基转移酶和NAD糖水解酶活性。 使用胍丁胺作为ADP-核糖受体， 主要是ADP-核糖基转移酶，而转移酶和NAD 重组Yac-2蛋白的糖水解酶活性相似。 推导的Yac-2转移酶的氨基酸序列包含 几种细菌毒素和哺乳动物毒素共有的共有区 转移酶和NAD糖水解酶，与以下假设一致， 在ADP-1和ADP-2中，NAD的结合和催化有一个共同的机制， 核糖基转移酶。

Mono-ADP-ribosylation, a posttranslational modification of proteins in which the ADP-ribose moiety of NAD is transferred to proteins, is responsible for the toxicity of some bacterial toxins (e.g., cholera toxin, pertussis toxin). NAD:arginine ADP-ribosyltransferases cloned from human and rabbit skeletal muscle and from mouse lymphoma cells (Yac- 1 ADP-ribosyltransferase), are glycosylphosphatidylinositol (GPI)- anchored and have similar enzymatic and physical properties. A second ADP-ribosyltransferase (Yac-2) was cloned from mouse lymphoma cells, which differs in properties from the previously identified eukaryotic transferases. The nucleotide and deduced amino acid sequences of the Yac-1 and Yac-2 transferases are 58 and 33% identical, respectively. The Yac-2 protein is membrane-bound but, unlike the Yac-1 enzyme, appears not to be GPI-anchored. The Yac-1 and Yac-2 enzymes, expressed as glutathione-S-transferase fusion proteins in E. coli, were used to compare their ADP-ribosyltransferase and NAD glycohydrolase activities. Using agmatine as the ADP-ribose acceptor, the Yac-1 enzyme was predominantly an ADP-ribosyltransferase, whereas the transferase and NAD glycohydrolase activities of the recombinant Yac-2 protein were similar. The deduced amino acid sequence of the Yac-2 transferase contained consensus regions common to several bacterial toxin and mammalian transferases and NAD glycohydrolases, consistent with the hypothesis that there is a common mechanism of NAD binding and catalysis among ADP- ribosyltransferases.