Physiological role of endogenous mono (ADP-ribosyl) ation of GTP binding proteins

以聚精氨酸为ADP-核糖受体，从人血小板中纯化了三种精氨酸特异性ADP-核糖基转移酶，命名为ADP-核糖基转移酶A。当人血小板膜在[32 P]-NAD存在下与转移酶A孵育时，特异性标记45 K膜蛋白。通过强阴离子交换HPLC分析磷酸二酯酶标记产物时，90%以上的放射性以5 '-AMP形式被去除。单（ADP-核糖）和45 K蛋白之间的连接对中性羟胺处理敏感。当膜被敌草虫毒素预ADP-核糖基化时，该酶将ADP-核糖转移到45 K蛋白被抑制。这些结果表明，ADP-核糖基转移酶AI催化单（ADP-核糖基）化的特定膜G蛋白，GS。孵育的血小板膜与转移酶AI导致腺苷酸环化酶系统的激活。结果表明，ADP-核糖基转移酶AI通过内源性单（ADP-核糖基）氧化PG进一步调节腺苷酸环化酶系统。

Three types of arginine-specific ADP-ribosyltransferase, named ADP-ribosyltransferase A, were purified from human platelets using polyarginine as an ADP-ribose acceptor. When human platelet membranes were incubated with the transferase A in the presence of [32P]-NAD, a 45 K Membrane protein was specifically labeled. On the analysis of labeled product with phosphodiesterase by strong-anion exchange HPLC, more than 90% of the radioactivity was deleted as 5'-AMP. The linkage between mono (ADP-ribose) and 45K protein was sensitive to neutral hydroxylamine treatment. ADP-ribose transfer to 45K protein by this enzyme was suppressed when membranes were pre-ADP-ribosylated by chlera toxin. These results suggest that the ADP-ribosyltransferase AI catalyzes mono (ADP-ribosyl) ation of the specific membrane G protein, Gs.Incubation of platelet membranes with the transferase AI resulted in activation of the adenylate cyclase system. This stimulatory effects of the transferase AI on the adenylate cyclase system was further enhanced by prostagrandin (PG) El treatment.These results indicate a role of ADP-ribosyltransferase AI in regulation of the adentlate cyclase system via endogenous mono (ADP-ribosyl) ation og Gs.