Nakata H, Fujisawa H
Department of Biochemistry, Asahikawa Medical College, Hokkaido.
J Biochem. 1988 Sep;104(3):457-60. doi: 10.1093/oxfordjournals.jbchem.a122489.
Rat pheochromocytoma PC 12 cell membranes were shown to possess A2-like adenosine binding sites as assessed by using 5'-N-ethylcarboxamide[3H]adenosine [( 3H]NECA). Specific [3H]NECA binding to PC 12 cell membrane at 0 degrees C was saturable and showed a monophasic saturation profile. In contrast, [3H]NECA binding to PC 12 cell membrane at 30 degrees C exhibited a biphasic profile suggesting the presence of two specific binding site. The rank order of potency for inhibition of [3H]NECA binding at 0 degrees C was NECA greater than 2-chloroadenosine greater than 2',5'-dideoxyadenosine greater than isobutylmethylxanthine much greater than phenylisopropyladenosine. These adenosine binding sites were solubilized with sodium cholate and the solubilized portion retained the same ligand binding characteristics as those of the membrane-bound form. Gel filtration experiments indicated an apparent Stokes radius of 6.7 nm for these adenosine binding sites/detergent complexes.
通过使用5'-N-乙基羧酰胺[³H]腺苷[（³H]NECA）评估，发现大鼠嗜铬细胞瘤PC 12细胞膜具有A2样腺苷结合位点。在0℃时，[³H]NECA与PC 12细胞膜的特异性结合是可饱和的，并呈现单相饱和曲线。相比之下，在30℃时，[³H]NECA与PC 12细胞膜的结合呈现双相曲线，表明存在两个特异性结合位点。在0℃时抑制[³H]NECA结合的效力顺序为NECA＞2-氯腺苷＞2'，5'-二脱氧腺苷＞异丁基甲基黄嘌呤＞苯异丙基腺苷。这些腺苷结合位点用胆酸钠增溶，增溶部分保留了与膜结合形式相同的配体结合特性。凝胶过滤实验表明，这些腺苷结合位点/去污剂复合物的表观斯托克斯半径为6.7nm。
