GTP BINDING PROTEINS AND ADENYLATE CYCLASE

霍乱毒素，霍乱弧菌的分泌产物 对毁灭性的腹泻综合征特征负有部分责任 霍乱时，通过催化ADP-核糖化激活腺酰环化酶 的刺激性鸟嘌呤核苷酸结合蛋白。 循环酶系统。毒素催化的反应被刺激，在 GTP的存在，约20 kDa的鸟嘌呤核苷酸结合 蛋白质，称为ADP核糖化因子或ARF。兔多克隆 抗牛sARF II抗体可与可溶性和膜型ARF反应 但不与其他几种鸟嘌呤核苷酸结合蛋白反应。 抗ARF抗体与大约20 kDa的ARF样蛋白发生反应 在几个物种的各种组织中。最高水平的 在脑组织和其他神经组织中观察到免疫反应。在其他 组织中有一条与SARF I相对应的免疫反应条带。 在大鼠大脑发育过程中，当通过免疫反应和 功能，SARF II在出生时最低，10天后略有增加， 在27-60天达到最大值；SARF I不变。SARF II的增加 出生后发育中的蛋白质与ARF3mRNA的增加是平行的 但不是通过其他五个ARF的mRNAs。 在GTP-γ-S存在下，ARF和毒素形成了一个 在十二烷基硫酸钠(十二烷基硫酸钠)中的ArF-CTA络合物或在DMPC/胆酸盐中的自缔合ArF，其 通过凝胶过滤从单体ARF和CTA中分离得到。底物 ARF/毒素复合体的特异性不同于 单体蛋白质。 ARF-3基因由5个外显子和4个内含子组成 18.3kb。用交替多聚腺苷法合成了两个arf 3mRNAs 外显子5中的信号。该基因似乎有多个转录开始 5‘启动子区域没有TATA盒、CAAT盒和高G/C含量。 ARF 1基因与ARF 3基因完全相同，只是它只有一个 多聚腺苷基化信号。ARF2基因的组织结构是相同的 与ARF 1和ARF 3的那些相比，尽管启动子区域有点 不同的ARF-2基因转录调控可能不同。

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. The toxin-catalyzed reaction is stimulated, in the presence of GTP, by approximately 20 kDa guanine nucleotide-binding proteins, termed ADP-ribosylation factors or ARFs. Rabbit polyclonal antibodies against bovine sARF II reacted with soluble and membrane ARFs but did not react with several other guanine nucleotide-binding proteins. The anti-ARF antibodies reacted with approximately 20 kDa ARF-like proteins in a variety of tissues from several species. The highest levels of immunoreactivity were observed in brain and other neural tissues. In other tissues, an immunoreactive band corresponding to SARF I was present. During rat brain development, when quantified by both immunoreactivity and function, SARF II was lowest at birth, increased somewhat by 10 days, and was maximal at 27-60 days; SARF I was unchanged. The increase of SARF II protein during postnatal development was paralleled by increased ARF 3 mRNA but not by mRNAs for five other ARFs. In the presence of GTP-gamma-S, ARF and toxin formed either an ARF-CTA complex in SDS (SDS) or self-associated ARF in DMPC/cholate, which were separated from monomeric ARF and CTA by gel filtration. Substrate specificities of ARF/toxin complexes were different from those of the monomeric proteins. The ARF 3 gene contains five exons and four introns and spans 18.3 kb. Two ARF 3 mRNAs are synthesized using alternative polyadenylation signals in exon 5. The gene appears to have multiple transcription start sites, no TATA box, no CAAT box and high G/C content in 5' promotor region. The ARF 1 gene is identical to the ARF 3 except that it has only one polyadenylation signal. The organization of the ARF 2 gene is identical to those of ARFs 1 and 3, although the promoter region is somewhat different and thus regulation of ARF 2 gene transcription may differ.