CHARACTERIZATION OF MAMMALIAN ADP-RIBOSLYTRANSFERASES

单-ADP-核糖化，蛋白质的翻译后修饰 NAD的ADP-核糖部分被转移到蛋白质上，是 对某些细菌毒素(如霍乱)的毒性负责 百日咳毒素)。NAD：精氨酸ADP-核糖基转移酶克隆 从人和兔的骨骼肌以及从小鼠淋巴瘤细胞(YAc- 1 ADP-核糖基转移酶)，是糖基磷脂酰肌醇(GPI)- 锚定并具有相似的酶和物理性质。一秒钟 从小鼠淋巴瘤细胞中克隆了腺苷二磷酸核糖转移酶(YAc-2)， 它在性质上与先前鉴定的真核生物不同 转移酶。该基因的核苷酸序列和推导的氨基酸序列 Yac-1和Yac-2转移酶分别有58%和33%的同源性。这个 Yac-2蛋白是膜结合的，但与Yac-1酶不同，似乎不是 将被GPI锚定。Yac-1和Yac-2酶，表达为 谷胱甘肽-S-转移酶融合蛋白在大肠杆菌中的表达 比较它们的ADP-核糖基转移酶和NAD糖水解酶活性。 以胍丁胺为ADP-核糖受体，YAc-1酶. 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。 Yac-2转移酶推导的氨基酸序列包含 几种细菌毒素和哺乳动物的共同区域 转移酶和NAD糖水解酶，与假设一致 ADP与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.