Schmidt G J, Huber L J, Weiter J J
Eye Research Institute of Retina Foundation, Boston, Massachusetts 02114.
J Biol Chem. 1987 Oct 15;262(29):14333-6.
A 20-kilodalton adenosine nucleotide-binding protein (A-protein) extracted from rod outer segments is shown to catalyze the cholera toxin-mediated ADP-ribosylation of GTP-binding protein (G-protein) from the outer segment. Radiolabel from [adenylate-32P] NAD+ was associated specifically with both the alpha-subunit of G-protein and with A-protein in the presence of activated cholera toxin. In the absence of added A-protein, G-protein appears to undergo ADP-ribosylation at a slower rate. In the absence of G-protein, A-protein was found to be labeled following incubation with [adenylate-32P]NAD+ and cholera toxin. In the presence of G-protein, a light-dependent component of A-protein labeling was observed. A-protein is a labile component of rod outer segments and has an affinity for ADP. The findings suggest that A-protein may act as an ADP-ribosyltransferase in the cholera toxin-mediated ADP-ribosylation of G-protein.
从视杆细胞外段提取的一种20千道尔顿的腺苷酸结合蛋白（A蛋白），被证明能催化霍乱毒素介导的视杆细胞外段GTP结合蛋白（G蛋白）的ADP核糖基化。在活化的霍乱毒素存在的情况下，[腺苷酸 - 32P]NAD⁺的放射性标记物特异性地与G蛋白的α亚基以及A蛋白结合。在没有添加A蛋白的情况下，G蛋白似乎以较慢的速率进行ADP核糖基化。在没有G蛋白的情况下，发现A蛋白在与[腺苷酸 - 32P]NAD⁺和霍乱毒素孵育后被标记。在有G蛋白存在的情况下，观察到A蛋白标记存在光依赖性成分。A蛋白是视杆细胞外段的一种不稳定成分，对ADP有亲和力。这些发现表明，A蛋白可能在霍乱毒素介导的G蛋白ADP核糖基化过程中充当ADP核糖基转移酶。
