Cui L, Bingham S E, Kuhn M, Käss H, Lubitz W, Webber A N
Department of Botany, Arizona State University, Tempe 85287-1601.
Biochemistry. 1995 Feb 7;34(5):1549-58. doi: 10.1021/bi00005a011.
The chloroplast psaB gene encodes one of the polypeptides of the photosystem I reaction center heterodimer that coordinates the electron transfer components P700, A0, and A1. Histidine residues in the most highly conserved region of the PsaB protein are predicted to coordinate the P700 reaction center chlorophyll(s) and the initial electron acceptor, A0. Oligonucleotide-mediated site-directed mutagenesis and chloroplast transformation of Chlamydomonas reinhardtii have been used to determine the importance of these conserved histidines in photosystem I reaction center biogenesis and function. It is demonstrated that these histidine residues are essential for stable accumulation of the photosystem I reaction center. Protein pulse-labeling shows that changing the histidine residues impairs a post-translational step in reaction center assembly. Photosystem I complexes from the mutants have been characterized by Electron Nuclear Double Resonance and Electron Spin Echo Envelope Modulation spectroscopy to determine the impact of any mutations on P700+. In all cases we determine that spectroscopic characteristics of P700+ remain unchanged. The implications of these results to current models of the photosystem I reaction center and related bacterial reaction centers are discussed.
叶绿体psaB基因编码光系统I反应中心异二聚体的一种多肽，该异二聚体协调电子传递成分P700、A0和A1。预计PsaB蛋白最保守区域中的组氨酸残基可协调P700反应中心叶绿素和初始电子受体A0。莱茵衣藻的寡核苷酸介导的定点诱变和叶绿体转化已用于确定这些保守组氨酸在光系统I反应中心生物发生和功能中的重要性。结果表明，这些组氨酸残基对于光系统I反应中心的稳定积累至关重要。蛋白质脉冲标记表明，改变组氨酸残基会损害反应中心组装中的翻译后步骤。已通过电子核双共振和电子自旋回波包络调制光谱对突变体的光系统I复合物进行了表征，以确定任何突变对P700+的影响。在所有情况下，我们都确定P700+的光谱特征保持不变。讨论了这些结果对当前光系统I反应中心模型和相关细菌反应中心的影响。
