Malyan A N
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Biochemistry (Mosc). 2002 Nov;67(11):1253-7. doi: 10.1023/a:1021301421724.
A kinetic analysis of ATP binding to noncatalytic sites of chloroplast coupling factor CF1 was made. The ATP binding proved to be unaffected by reduction of the disulfide bridge of the CF1 gamma-subunit. The first-order equation describing nucleotide binding to noncatalytic sites allowed for two vacant nucleotide binding sites different in their kinetics. As suggested by nucleotide concentration dependence of the rate of nucleotide binding, the tight binding was preceded by rapid reversible binding of nucleotides. Preincubation of CF1 with Mg2+ resulted in a decreased rate of ATP binding. ATP dissociation from noncatalytic sites was described by the first order equation for similar sites with a dissociation rate constant kd(ATP) approximately/= 10-3 min-1. Noncatalytic sites of CF1 were shown to be not homogeneous. One of them retained the major part of endogenous ADP after precipitation of CF1 with ammonium sulfate. Its two other sites differed in kinetic parameters and affinity for ATP. Anions of phosphate, sulfite, and especially, pyrophosphate inhibited the interaction between ATP and the noncatalytic sites.
对ATP与叶绿体偶联因子CF1非催化位点的结合进行了动力学分析。结果表明,CF1γ亚基二硫键的还原对ATP结合没有影响。描述核苷酸与非催化位点结合的一级方程表明,存在两个动力学不同的空核苷酸结合位点。根据核苷酸结合速率对核苷酸浓度的依赖性可知,在紧密结合之前,核苷酸会先进行快速可逆结合。CF1与Mg2+预孵育会导致ATP结合速率降低。ATP从非催化位点的解离可用类似位点的一级方程描述,解离速率常数kd(ATP)约为10-3 min-1。结果表明,CF1的非催化位点并非均一。在用硫酸铵沉淀CF1后,其中一个位点保留了大部分内源性ADP。另外两个位点的动力学参数和对ATP的亲和力有所不同。磷酸根、亚硫酸根,尤其是焦磷酸根阴离子会抑制ATP与非催化位点之间的相互作用。