Klimov V V, Baranov S V
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, 142290, Moscow Region, Russia.
Biochim Biophys Acta. 2001 Jan 5;1503(1-2):187-96. doi: 10.1016/s0005-2728(00)00222-x.
It is well established that bicarbonate stimulates electron transfer between the primary and secondary electron acceptors, Q(A) and Q(B), in formate-inhibited photosystem II; the non-heme Fe between Q(A) and Q(B) plays an essential role in the bicarbonate binding. Strong evidence of a bicarbonate requirement for the water-oxidizing complex (WOC), both O2 evolving and assembling from apo-WOC and Mn2+, of photosystem II (PSII) preparations has been presented in a number of publications during the last 5 years. The following explanations for the involvement of bicarbonate in the events on the donor side of PSII are considered: (1) bicarbonate serves as an electron donor (alternative to water or as a way of involvement of water molecules in the oxidative reactions) to the Mn-containing O2 center; (2) bicarbonate facilitates reassembly of the WOC from apo-WOC and Mn2+ due to formation of the complexes MnHCO3+ and Mn(HCO3)2 leading to an easier oxidation of Mn2+ with PSII; (3) bicarbonate is an integral component of the WOC essential for its function and stability; it may be considered a direct ligand to the Mn cluster; (4) the WOC is stabilized by bicarbonate through its binding to other components of PSII.
众所周知，在甲酸盐抑制的光系统II中，碳酸氢盐可刺激初级和次级电子受体Q(A)和Q(B)之间的电子转移；Q(A)和Q(B)之间的非血红素铁在碳酸氢盐结合中起重要作用。在过去5年的许多出版物中，都有强有力的证据表明，光系统II（PSII）制剂的水氧化复合物（WOC）（从脱辅基WOC和Mn2+进化并组装产生O2）需要碳酸氢盐。对于碳酸氢盐参与PSII供体侧事件，有以下几种解释：（1）碳酸氢盐作为含锰O2中心的电子供体（替代水或作为水分子参与氧化反应的一种方式）；（2）由于形成了MnHCO3+和Mn(HCO3)2复合物，碳酸氢盐促进了脱辅基WOC和Mn2+重新组装形成WOC，从而使Mn2+更容易被PSII氧化；（3）碳酸氢盐是WOC发挥功能和保持稳定所必需的一个组成部分；它可被视为锰簇的直接配体；（4）碳酸氢盐通过与PSII的其他成分结合来稳定WOC。
