Two guanine nucleotide-binding proteins in rat brain serving as the specific substrate of islet-activating protein, pertussis toxin. Interaction of the alpha-subunits with beta gamma-subunits in development of their biological activities.
Two guanine nucleotide-binding proteins in rat brain serving as the specific substrate of islet-activating protein, pertussis toxin. Interaction of the alpha-subunits with beta gamma-subunits in development of their biological activities.
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大鼠脑中的两种鸟嘌呤核苷酸结合蛋白作为胰岛激活蛋白、百日咳毒素的特异性底物。
DOI：
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发表时间：
1986
影响因子：
4.8
通讯作者：
M. Ui
中科院分区：
文献类型：
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作者：
T. Katada;M. Oinuma;M. Ui
从大鼠脑膜胆酸盐提取物中纯化了两种蛋白质，它们可作为胰岛激活蛋白（IAP）、百日咳毒素和高亲和力结合鸟苷5 ′-（3-O-硫代）三磷酸（GTP γ S）催化ADP-核糖基化的底物。纯化的蛋白质具有与先前从兔肝和牛脑中纯化的IAP底物相同的异源三聚体结构（α β γ），并且仅在α方面彼此不同; α的分子量为41，000（α 41 β γ）和39，000（α 39 β γ）。将两者进一步拆分为α（α 41或α 39）和β γ，也将其纯化至均一以比较α-单体与原始三聚体的活性。在不存在Mg 2+的情况下，通过将α 41或α 39与β γ结合来维持刚性三聚体结构对于α亚基被IAP进行ADP核糖基化是必不可少的。α-亚基非常稳定，但在这些条件下仅显示部分GTP γ S-结合活性。当在亚微摩尔Mg 2+存在下测定时，分离的α-单体表现出高的GTdR活性，但在30 ° C下非常不稳定，并且不被IAP ADP-核糖基化。GTP γ S与α-亚基结合的最有利条件是通过在毫摩尔Mg 2+存在下将α 41或α 39与β γ结合来实现的，这可能是由于稳定性的增加和GTP结合位点的暴露。α 41 β γ（α 41）和α 39 β γ（α 39）之间的这些性质没有定性差异。但α 39 β γ（或α 39）通常比α 41 β γ（或α 41）更活跃，至少部分原因是其对Mg 2+的亲和力较高，对β γ的亲和力较低。这些差异之间的活动α 41 β γ和α 39 β γ的信号转导的生理作用的关系进行了讨论。
Two proteins serving as substrates for ADP-ribosylation catalyzed by islet-activating protein (IAP), pertussis toxin, and binding guanosine 5'-(3-O-thio)triphosphate (GTP gamma S) with high affinities were purified from the cholate extract of rat brain membranes. The purified proteins had the same heterotrimeric structure (alpha beta gamma) as the IAP substrates previously purified from rabbit liver and bovine brain and differed from each other in alpha only; the molecular weight of alpha was 41,000 (alpha 41 beta gamma) and 39,000 (alpha 39 beta gamma). Both were further resolved into alpha (alpha 41 or alpha 39) and beta gamma which were also purified to homogeneity to compare the activities of alpha-monomers with the original trimers. The maintenance of the rigid trimeric structure by combining alpha 41 or alpha 39 with beta gamma in the absence of Mg2+ was essential for the alpha-subunit to be ADP-ribosylated by IAP. The alpha-subunit was very stable but displayed the only partial GTP gamma S-binding activity under these conditions. Isolated alpha-monomers exhibited high GTPase activities when assayed in the presence of submicromolar Mg2+ but were very unstable at 30 degrees C and not ADP-ribosylated by IAP. The most favorable conditions for the GTP gamma S binding to alpha-subunits were achieved by combining alpha 41 or alpha 39 with beta gamma in the presence of millimolar Mg2+, probably due to the increase in stability and unmasking of the GTP-binding sites. There was no qualitative difference in these properties between alpha 41 beta gamma (alpha 41) and alpha 39 beta gamma (alpha 39). But alpha 39 beta gamma (or alpha 39) was usually more active than alpha 41 beta gamma (or alpha 41), at least partly due to its higher affinity for Mg2+ and lower affinity for beta gamma. Relation of these differences in activity between alpha 41 beta gamma and alpha 39 beta gamma to their physiological roles in signal transduction is discussed.