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对氢键网络的干扰降低细胞色素b6f复合体中Chla的光稳定性

DOI: 10.1360/N052014-00173, PP. 311-316

Keywords: 叶绿素a,光稳定性,氢键,定点突变,细胞色素b6f蛋白复合体

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Abstract:

细胞色素b6f蛋白复合体(Cytb6f)参与光合膜上电子传递和跨膜质子转移,在体内以二体形式存在,每个单体只结合1分子叶绿素a(Chla).该Chla性质独特,光照条件下十分稳定,是甲醇中游离Chla的120~130倍,然而其光稳定性的机制仍未彻底阐明.Cytb6f2.7?的晶体结构显示,Chla中心的Mg离子和H2O分子配位,并且该H2O分子通过氢键与复合体亚基Ⅳ的氨基酸G136和T137相互作用.本研究基于这一结构特点,对上述2个氨基酸进行了定点突变,以干扰、破坏氢键网络.结果发现,突变不仅导致蛋白与Chla结合能力下降,而且显著降低了Chla的光稳定性,这一结果表明,Cytb6f中Chla相关的氢键网络对其稳定性具有重要的作用.

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