...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >STUDIES OF CA2+ BINDING IN SPINACH PHOTOSYSTEM II USING CA-45(2+)
【24h】

STUDIES OF CA2+ BINDING IN SPINACH PHOTOSYSTEM II USING CA-45(2+)

机译：利用CA-45（2+）研究菠菜光系统中的CA2 +结合

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 Ca2+-binding properties of photosystem II were investigated with radioactive Ca-45(2+). PS II membranes, isolated from spinach grown on a medium containing Ca-45(2+), contained 1.5 Ca2+ per PS II unit. Approximately half of the incorporated radioactivity was lost after incubation for 30 h in nonradioactive buffer. About 1 Ca2+/PS II bound slowly to Ca2+-depleted membranes in the presence of the extrinsic 16- and 23-kDa polypeptides in parallel with restoration of oxygen-evolving activity. The binding was heterogeneous with dissociation constants of 60 mu M (0.7 Ca2+/PS II) and 1.7 mM (0.3 Ca2+/PS II), respectively, which could reflect different affinities of the dark-stable S-states for Ca2+. The reactivation of oxygen-evolving activity closely followed the binding of Ca2+, showing that a single exchangeable Ca2+ per PS II is sufficient for the water-splitting reaction to function. In PS II, depleted of the 16- and 23-kDa polypeptides, about 0.7 exchangeable Ca2+/PS II binds with a dissociation constant of 26 mu M, while 0.3 Ca2+ binds with a much weaker affinity (K-d > 0.5 mM). The rate of binding of Ca2+ in the absence of the two extrinsic polypeptides was significantly higher than with the polypeptides bound. The rate of dissociation of bound Ca2+ in the dark, which had a half-time of about 80 h in intact PS II, increased in the absence of the 16- and 23-kDa polypeptides and showed a further increase after the additional removal of the 33-kDa protein and manganese. The rate of dissociation was also significantly faster in weak light than in the dark regardless of the presence or absence of the 16- and 23-kDa polypeptides. Removal of the 33-kDa donor-side polypeptide together with the two lighter ones led to a reduction in the amount of bound Ca2+, while practically no Ca2+ bound after treatments to dissociate also the manganese of the water-oxidizing site. [References: 34]
机译：用放射性Ca-45（2+）研究了光系统II的Ca2 +结合特性。从生长在含Ca-45（2+）的培养基上的菠菜中分离出的PS II膜，每个PS II单元含1.5 Ca2 +。在非放射性缓冲液中孵育30小时后，大约一半的结合放射活性消失。在存在非本征的16kDa和23kDa多肽的情况下，大约有1个Ca2 + / PS II缓慢结合到贫Ca2 +的膜上，同时恢复了放氧活性。结合是异质的，解离常数分别为60μM（0.7 Ca2 + / PS II）和1.7 mM（0.3 Ca2 + / PS II），这可能反映了Ca2 +的暗稳定S状态的不同亲和力。放氧活性的重新激活紧随Ca2 +的结合，表明每个PS II单个可交换的Ca2 +足以使水分解反应起作用。在PS II中，耗尽了16-kDa和23-kDa的多肽后，约有0.7个可交换的Ca2 + / PSII以26μM的解离常数结合，而0.3 Ca2 +则以弱得多的亲和力结合（K-d> 0.5 mM）。在不存在两个外部多肽的情况下，Ca 2+的结合速率显着高于结合的多肽。在黑暗中结合Ca2 +的解离速率在完整的PS II中大约有80小时的半衰期，在不存在16-kDa和23-kDa多肽的情况下，解离速率增加，并且在进一步去除Ck +后，解离速率进一步增加。 33 kDa蛋白质和锰。无论存在或不存在16-kDa和23-kDa多肽，弱光下的解离速率也比暗处快得多。除去33-kDa供体侧多肽以及两个较轻的多肽导致结合的Ca 2+的量减少，而实际上在处理以使水氧化位点的锰解离后，没有结合的Ca 2+。 [参考：34]

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