Shoshan V, Strotmann H
J Biol Chem. 1980 Feb 10;255(3):996-9.
The effects of phosphate on the energy-dependent exchange of the tightly bound adenine nucleotides in chloroplast thylakoids has been studied. 1. Phosphate was found to have a dual effect on ADP binding; at low light intensities Pi enhanced the rate of binding and the total amount of tightly bound ADP, while at saturating light intensities, it decreased the level of bound nucleotides. Half-maximal stimulation or inhibition of ADP binding occurred at about 30 microM phosphate. 2. Phosphate inhibition of ADP binding at saturating light intensities is prevented in the presence of an ADP-regenerating system. Pi had no effect on the amount of ATP bound to chloroplast coupling factor 1 (CF1), which was lower than the amount of ADP bound. 3. Arsenate acted similarly to phosphate at low light intensities but not at saturating light intensities. 4. At low light intensities the interaction of phosphate with the membrane-bound CF1 increased the binding affinity for ADP about 8-fold. 5. Kinetic analysis of the ADP binding showed that phosphate increased the rate constant for ADP binding to the adenine nucleotide-depleted form of CF1.
已对磷酸盐对叶绿体类囊体中紧密结合的腺嘌呤核苷酸的能量依赖性交换的影响进行了研究。1. 发现磷酸盐对ADP结合有双重作用；在低光照强度下，磷酸增强了结合速率和紧密结合的ADP总量，而在饱和光照强度下，它降低了结合核苷酸的水平。ADP结合的半数最大刺激或抑制发生在约30微摩尔磷酸盐时。2. 在存在ADP再生系统的情况下，可防止磷酸盐在饱和光照强度下对ADP结合的抑制。磷酸对与叶绿体偶联因子1（CF1）结合的ATP量没有影响，其低于结合的ADP量。3. 在低光照强度下，砷酸盐的作用与磷酸盐相似，但在饱和光照强度下则不然。4. 在低光照强度下，磷酸盐与膜结合的CF1的相互作用使对ADP的结合亲和力增加了约8倍。5. ADP结合的动力学分析表明，磷酸盐增加了ADP与CF1的腺嘌呤核苷酸耗尽形式结合时的速率常数。
