Regel R E, Ivleva N B, Zer H, Meurer J, Shestakov S V, Herrmann R G, Pakrasi H B, Ohad I
Botanisches Institute, Ludwig-Maximilians-University, Menzinger Str. 67, D-80638 München, Germany.
J Biol Chem. 2001 Nov 2;276(44):41473-8. doi: 10.1074/jbc.M102007200. Epub 2001 Aug 23.
The photosystem II (PSII) complex of photosynthetic oxygen evolving membranes comprises a number of small proteins whose functions remain unknown. Here we report that the low molecular weight protein encoded by the psbJ gene is an intrinsic component of the PSII complex. Fluorescence kinetics, oxygen flash yield, and thermoluminescence measurements indicate that inactivation of the psbJ gene in Synechocystis 6803 cells and tobacco chloroplasts lowers PSII-mediated oxygen evolution activity and increases the lifetime of the reduced primary acceptor Q(A)(-) (more than a 100-fold in the tobacco DeltapsbJ mutant). The decay of the oxidized S(2,3) states of the oxygen-evolving complex is considerably accelerated, and the oscillations of the Q(B)(-)/S(2,3) recombination with the number of exciting flashes are damped. Thus, PSII can be assembled in the absence of PsbJ. However, the forward electron flow from Q(A)(-) to plastoquinone and back electron flow to the oxidized Mn cluster of the donor side are deregulated in the absence of PsbJ, thereby affecting the efficiency of PSII electron flow following the charge separation process.
光合放氧膜的光系统II（PSII）复合物包含一些功能未知的小蛋白。在此我们报告，由psbJ基因编码的低分子量蛋白是PSII复合物的一个内在组分。荧光动力学、氧闪产率和热发光测量表明，集胞藻6803细胞和烟草叶绿体中psbJ基因的失活降低了PSII介导的放氧活性，并增加了还原态初级受体Q(A)(-)的寿命（烟草DeltapsbJ突变体中增加了100多倍）。放氧复合物氧化态S(2,3)状态的衰减显著加快，并且Q(B)(-)/S(2,3)复合与激发闪光次数的振荡受到抑制。因此，PSII可以在没有PsbJ的情况下组装。然而，在没有PsbJ的情况下，从Q(A)(-)到质体醌的正向电子流以及回到供体侧氧化态锰簇的反向电子流会失调，从而影响电荷分离过程后PSII电子流的效率。
