...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >LASER FLASH ABSORPTION SPECTROSCOPY STUDY OF FERREDOXIN REDUCTION BY PHOTOSYSTEM I - SPECTRAL AND KINETIC EVIDENCE FOR THE EXISTENCE OF SEVERAL PHOTOSYSTEM I FERREDOXIN COMPLEXES
【24h】

LASER FLASH ABSORPTION SPECTROSCOPY STUDY OF FERREDOXIN REDUCTION BY PHOTOSYSTEM I - SPECTRAL AND KINETIC EVIDENCE FOR THE EXISTENCE OF SEVERAL PHOTOSYSTEM I FERREDOXIN COMPLEXES

机译：光系统I还原铁氧还蛋白的激光吸收光谱研究-存在多个光系统I铁氧还蛋白复合物的光谱和运动学证据

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The existence of three first-order phases has been previously reported for the reduction of soluble ferredoxin by photosystem I (PSI), both from the cyanobacterium Synechocystis sp. PCC 6803 (at pH 8 and in the presence of salts) [Setif, P. Q. Y., & Bottin, H. (1994) Biochemistry 33, 8495-8504]. The spectra of these three phases (t(1/2) < 1 mu s, = 13-20 and 103-123 mu s) have been measured between 460 and 600 nm. All of them are fully consistent with electron transfer from (F-A,F-B)(-), the terminal 4Fe-4S accepters of PSI, to ferredoxin, Though the three spectra deviate significantly from the spectrum that can be calculated independently for this process, their sum closely matches the calculated spectrum. A detailed examination of these deviations indicates that the intermediate (13-20 mu s) and slow (103-123 mu s) first-order phases are associated with two distinct ferredoxin-binding sites on PSI. Under the same conditions, a fourth phase of negative amplitude is also observed in the 460-600 nm region, It is ascribed to reoxidation of reduced ferredoxin by an unknown species. The kinetic properties of this process show that it is triggered by collision of free ferredoxin with a preformed PSI-ferredoxin complex, Taking this reaction into account, it is shown that the relative proportions of the three first-order phases of ferredoxin reduction do not depend upon the ferredoxin concentration, indicating that the different sites of ferredoxin binding are mutually exclusive, The kinetics of ferredoxin reduction were also studied at pH 5.8, in the absence of salts. Under these conditions, the affinity of ferredoxin for PSI is much higher than at pH 8 (dissociation constant approximate to 0.05 mu M versus 0.6 mu M) and the kinetics of ferredoxin reduction are much faster (a major submicrosecond phase and a single first-order microsecond phase with t(1/2) approximate to 9 mu s), whereas a third, slower first-order phase is essentially absent, Two similar first-order components are found for the reduction of spinach ferredoxin by PSI from Synechocystis at pH 8, though the apparent dissociation constant for the latter system is larger (approximate to 5 mu M). Despite the different affinities of spinach and Synechocystis ferredoxins for the cyanobacterial PSI, similar second-order rate constants are found in both cases at pH 8 [(2-6) x 10(8) M(-1) s(-1)]. [References: 29]
机译：先前已经报道了存在三个一级相的情况，这两个瞬态都来自蓝藻集胞藻属（Synechocystis sp。）的光系统I（PSI）还原可溶性铁氧还蛋白。 PCC 6803（在pH 8和盐存在下）[Setif，P.Q.Y。，＆Bottin，H。（1994）Biochemistry 33，8495-8504]。这三个阶段的光谱（t（1/2）<1μs，= 13-20和103-123μs）已在460至600 nm之间测量。所有这些与从PSI的末端4Fe-4S受体（FA，FB）（-）到铁氧还蛋白的电子转移是完全一致的，尽管这三个光谱与该过程可以独立计算的光谱有很大的偏离，总和与计算的光谱非常匹配。对这些偏差的详细检查表明，中间（13-20μs）和缓慢（103-123μs）的一阶相与PSI上两个不同的铁氧还蛋白结合位点相关。在相同条件下，在460-600 nm区域内也观察到负振幅的第四相。这归因于还原的铁氧还蛋白被未知物种再氧化。该过程的动力学性质表明，它是由游离铁氧还蛋白与预先形成的PSI-铁氧还蛋白复合物的碰撞触发的。考虑到该反应，表明铁氧还蛋白还原的三个一级相的相对比例并不取决于根据铁氧还蛋白的浓度，表明铁氧还蛋白结合的不同位点是相互排斥的。还研究了在不存在盐的条件下在pH 5.8时铁氧还蛋白还原的动力学。在这些条件下，铁氧还蛋白对PSI的亲和力远高于在pH 8时（离解常数约为0.05μM对0.6μM），铁氧还蛋白还原的动力学要快得多（主要为亚微秒相和单个一阶微秒相，t（1/2）大约为9μs），而基本上没有第三相，较慢的一阶相。发现两个相似的一阶成分可通过pH值为8的集胞藻通过PSI还原菠菜铁氧还蛋白。 ，尽管后者系统的表观解离常数较大（约5μM）。尽管菠菜和球藻铁氧还蛋白对蓝细菌PSI的亲和力不同，但在两种情况下，在pH 8 [（2-6）x 10（8）M（-1）s（-1）时都发现了相似的二级速率常数。 。 [参考：29]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号