6-苄氨基嘌呤对叶绿体偶联因子功能的影响

Effect of 6-Benzylaminopurine on the Function of Coupling Factor 1

可溶性偶联因子经6-BA修饰后,明显促进Mg^(2+)-ATPase活力。从6-BA处理的叶绿体上洗脱下来的偶联因子,其Mg^(2+)-及Ca^(2+)-ATP酶活力都比对照有明显的增加。从~3H-6BA处理叶绿体上洗脱下来的偶联因子等蛋白,经聚丙烯酰胺电泳分析,~3H-6BA除与偶联因子结合外,还与RuBP羧化酶及其他蛋白结合。用6-BA处理提纯的β亚单位,能明显促进其Mg^(2+)-ATPase活力,表明6-BA至少有一个结合位点是在CF_1的β亚单位上并可影响其能量转换反应。

It has been shown that spinach chloroplasts preincubated with 6-benzylaminopurine (6-BA) showed higher photophosphorylation activities in both cyclic andnon-cyclic reaction systems at pH 7.2 and that the coupling efficiency was also improved by the 6-BA treatment (Huang et al. 1984). The effect of 6-BA on the function of soluble CF_1 and its binding sites on the chloroplasts was studied in this paper. The heat-activated Mg^(2+)-ATPase and Ca^(2+)-ATPase activities of CF_1 isolated from the chloroplasts treated with 6-BA were higher than those of control. The Mg^(2+)-ATPase activity was also increased when the soluble CF_1 was treated directly with 6-BA for 20 min before the heat-activation (Table 1, 9). These results suggest that the stimulatory effect of 6-BA is due to its interaction with CF_1. It was found by gel electrophoresis of proteins isolated from the chloroplasts treated with ~3H-6BA that ~3H-6BA was bound not only to CF_1, but also to RuBP-carboxylase and other minor protein bands. However, most of the ~3H-6BA was bound to GF_1 and RuBP-carboxylase (Table 3). The Mg^(2+)-ATPase activity of purified βsubunit (Fig. 1) was increased by treatment with ~3H-6BA as measured by using (γ-^(32)P)-ATP (Table 4). Our data suggest that 6-BA can-regulate CF_1 activation and that at least one of its binding sites on CF_1 is located at the β-subunit. These results may be of sigificance in studying the effect of cytokinin on photosynthesis.