GTP BINDING PROTEINS AND ADENYLATE CYCLASE

霍乱毒素，霍乱弧菌的分泌产物，部分原因是 对于霍乱这种毁灭性的腹泻综合征，激活 腺酰环化酶通过催化Gs(α)的ADP-核糖化， 循环酶系统的刺激性鸟嘌呤核苷酸结合蛋白。这 在GTP存在的情况下，毒素催化的反应被刺激约20% KDA鸟嘌呤核苷酸结合蛋白，称为ADP-核糖化因子或 ARF。从牛脑中分离到两种形式的arf，srf I和srf II。 胞浆。兔抗牛sRf II多克隆抗体与 可溶性和膜ARF，但不与其他鸟嘌呤反应 核苷酸结合蛋白，如20 kDa蛋白ras和 异三聚体转导G蛋白(例如，GT(α)，Gs(α)， Gi(Alpha)和Go(Alpha))。抗ARF抗体识别约20 kDa 在各种物种和器官系统中存在类似ARF的蛋白质。最高的 观察脑组织和其他神经组织的免疫反应水平。 在这些组织中观察到一对ARF双重体，其上带(Sarf II)。 占主导地位的形式。在其他组织中，一条免疫反应带 对应于低分子量物种(Sarf I)存在于 浓度更高。 ARF水平，当用免疫反应性来量化时，与 由功能测定确定，霍乱毒素催化的刺激 ADP-核糖化。在大鼠大脑发育过程中，当两者量化时 免疫反应性和功能，SARF II在出生时最低，显示出一些 第10天增加，27~60d最大，sRf-I无变化。 在脾和心脏中，Sarf I占优势；在脾中，Sarf II占优势 随着年龄的增长而增加，而在内心，它是减少的。基于这些研究，它 ARF蛋白似乎具有相同的表位，并且在不同的 在发育过程中的水平。

Cholera toxin, the secretory product of Vibrio cholerae responsible in part for the devastating diarrheal syndrome characteristic of cholera, activates adenylyl cyclase by catalyzing the ADP-ribosylation of Gs(alpha), the stimulatory guanine nucleotide-binding protein of the cyclase system. This toxin-catalyzed reaction is stimulated, in the presence of GTP, by about 20 kDa guanine nucleotidebinding proteins, termed ADP-ribosylation factors or ARFs. Two forms of ARF, sARF I and sARF II, were isolated from bovine brain cytosol. Rabbit polyclonal antibodies against bovine sARF II reacted with soluble and membrane ARFs but did not react with other guanine nucleotide-binding proteins such as the 20 kDa protein ras and the heterotrimeric transducing G proteins (e.g., Gt(alpha), Gs(alpha), Gi(alpha), and Go(alpha)). The anti-ARF antibodies recognized about 20 kDa ARF-like proteins in a variety of species and organ systems. The highest levels of immunoreactivity were observed in brain and other neural tissues. In these tissues an ARF doublet was observed, with the upper band (sARF II) being the predominant form. In other tissues, an immunoreactive band corresponding to the lower molecular weight species (sARF I) was present at higher concentration. Levels of ARF, when quantified by immunoreactivity, correlated with those determined by a functional assay, stimulation of cholera toxin-catalyzed ADP-ribosylation. During rat brain development, when quantified by both immunoreactivity and function, sARF II was lowest at birth, showed some increase at 10 days, and was maximal at 27-60 days; sARF I was unchanged. In spleen and heart, sARF I predominated over sARF II; in spleen, it increased with age while in heart, it decreased. Based on these studies, it appears that ARF proteins share epitopes and are expressed at different levels during development.