Purification and properties of the intact P-700 and Fx-containing Photosystem I core protein.
Purification and properties of the intact P-700 and Fx-containing Photosystem I core protein.
复制标题
完整的 P-700 和包含 Fx 的光系统 I 核心蛋白的纯化和特性。
DOI：
10.1016/s0005-2728(89)80439-6
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Golbeck,JH
中科院分区：
文献类型：
--
作者：
Parrett,KG;Mehari,T;Warren,PG;Golbeck,JH
完整的光系统I核心蛋白，含有psaA和psaB多肽，和电子传递组分P-700通过Fx，分离自蓝藻和高等植物光系统I复合物与离液剂，然后用蔗糖密度超离心。功能性去除8.9 kDa FA/FB多肽所需的NaClO 4、NaSCN、NaI、NaBr或尿素的浓度与离液剂的强度呈负相关。纯化至均一的光系统I核心蛋白含有4摩尔酸不稳定硫化物，并具有以下性质：（i）含Fx的核心由82和83 kDa反应中心多肽组成，但完全没有低分子量多肽;（ii）甲基紫精和其它联吡啶染料具有直接从Fx接受电子的能力;（iii）Fx在400 ~ 900 nm范围内的差谱是铁硫簇的特征，（iv）在室温下光学测定的Fx的中点电位比对照组正60 mV，（v）ESR谱表明Fx内部存在低温不均匀性;以及（vi）通过光谱学将不均匀性视为低温电子流到Fx的低效率。光系统I核心蛋白中非血红素铁和不稳定硫化物的量、psaA和psaB多肽的半胱氨酸含量以及高分子量多肽的化学计量所施加的限制使我们重新检查Fxis是由psaA和psaB异二聚体上的同源半胱氨酸残基连接的[4Fe-4S]而不是[2Fe-2S]簇的可能性。
The intact Photosystem I core protein, containing thepsaAandpsaBpolypeptides, and electron transfer components P-700 through Fx, was isolated from cyanobacterial and higher plant Photosystem I complexes with chaotropic agents followed by sucrose density ultracentrifugation. The concentrations of NaClO4, NaSCN, NaI, NaBr or urea required for the functional removal of the 8.9 kDa, FA/FBpolypeptide was shown to be inversely related to the strength of the chaotrope. The Photosystem I core protein, which was purified to homogeniety, contains 4 mol of acid-labile sulfide and has the following properties: (i) the Fx-containing core consists of the 82 and 83 kDa reaction center polypeptides but is totally devoid of the low-molecular-mass polypeptides; (ii) methyl viologen and other bipyridilium dyes have the ability to accept electrons directly from Fx; (iii) the difference spectrum of Fxfrom 400 to 900 nm is characteristic of an iron-sulfur cluster; (iv) the midpoint potential of Fx, determined optically at room temperature, is 60 mV more positive than in the control; (v) there is indication by ESR spectroscopy of low-temperature heterogeniety within Fx; and (vi) the heterogeneity is seen by optical spectroscopy as inefficiency in low-temperature electron flow to Fx. The constraints imposed by the amount of non-heme iron and labile sulfide in the Photosystem I core protein, the cysteine content of thepsaAandpsaBpolypeptides, and the stoichiometry of high-molecular-mass polypeptides, cause us to re-examine the possibility that Fxis a [4Fe-4S] rather than a [2Fe-2S] cluster ligated by homologous cysteine residues on thepsaAandpsaBheterodimer.