Adir N, Shochat S, Ohad I
Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
J Biol Chem. 1990 Jul 25;265(21):12563-8.
Light induces an irreversible modification of the photosystem II reaction center (RCII) affecting specifically one of its major components, the D1 protein (Ohad, I., Adir, N., Koike, H., Kyle, D. J., and Inoue, Y. I. (1990) J. Biol. Chem. 265, 1972-1979) which is degraded and replaced continuously (turnover). The turnover rate of D1 is related to light intensity. Evidence is presented showing that RCII translocates from the site of damage in the grana (appressed) domain of the chloroplast membranes to unappressed membrane domains where the D1 precursor protein (pD1) is translated and becomes integrated into RCII. Several forms of RCII (a, a*, and b) were identified on the basis of their electrophoretic mobility. pD1 was found only in the a and b forms in the unappressed membranes. Processing of pD1 occurs after its integration into RCII. Mature D1 appeared mostly in the a form of RCII and following its translocation to the appressed membrane domains also in the a* form. Thus the light intensity-dependent synthesis of D1 protein is related to the availability of modified RCII which serves as an acceptor for pD1. The shuttling of RCII between the two membrane domains may represent a control mechanism of thylakoid membrane protein synthesis.
光会诱导光系统II反应中心（RCII）发生不可逆修饰，特异性影响其主要成分之一——D1蛋白（奥哈德，I.，阿迪尔，N.，小池，H.，凯尔，D. J.，以及井上，Y. I.（1990年）《生物化学杂志》265卷，1972 - 1979页），该蛋白会持续降解并被替换（周转）。D1的周转速率与光强有关。有证据表明，RCII会从叶绿体膜基粒（紧密堆积）区域的损伤部位转移至非紧密堆积的膜区域，在那里D1前体蛋白（pD1）被翻译并整合到RCII中。根据电泳迁移率鉴定出了几种形式的RCII（a、a和b）。仅在非紧密堆积膜中的a和b形式中发现了pD1。pD1整合到RCII后会发生加工。成熟的D1大多以RCII的a形式出现，在其转移至紧密堆积膜区域后也会以a形式出现。因此，D1蛋白的光强依赖性合成与修饰后的RCII的可用性有关，后者作为pD1的受体。RCII在两个膜区域之间的穿梭可能代表了类囊体膜蛋白合成的一种控制机制。
