Mehta P, Jajoo A, Mathur S, Allakhverdiev S I, Bharti S
School of Life Sciences, Devi Ahilya University, Indore, 452017, India.
Biochemistry (Mosc). 2009 Jun;74(6):620-4. doi: 10.1134/s0006297909060054.
The effect of high salt concentration on photosystem II (PS II) electron transport rates and chlorophyll a fluorescence induction kinetics was investigated in coupled and uncoupled spinach thylakoid membranes. With increase in salt concentration, the rates of electron transport mediated by PS II and the F(v)/F(m) ratio were affected more in uncoupled thylakoids as compared to coupled thylakoid membranes. The uncoupled thylakoid membranes seemed to behave like coupled thylakoid membranes at high NaCl concentration (approximately 1 M). On increasing the salt concentration, the uncoupler was found to be less effective and Na+ probably worked as a coupling enhancer or uncoupling suppressor. We suggest that positive charge of Na+ mimics the function of positive charge of H+ in the thylakoid lumen in causing coupled state. The function of NaCl (monovalent cation) could be carried out by even lower concentration of Ca2+ (divalent cation) or Al3+ (trivalent cation). We conclude that this function of NaCl as coupling enhancer is not specific, and in general a positive charge is required for causing coupling in uncoupled thylakoid membranes.
在偶联和非偶联的菠菜类囊体膜中研究了高盐浓度对光系统II（PS II）电子传递速率和叶绿素a荧光诱导动力学的影响。随着盐浓度的增加，与偶联类囊体膜相比，非偶联类囊体膜中由PS II介导的电子传递速率和F(v)/F(m)比值受到的影响更大。在高NaCl浓度（约1 M）下，非偶联类囊体膜的行为似乎类似于偶联类囊体膜。随着盐浓度的增加，发现解偶联剂的效果变差，Na+可能起到了偶联增强剂或解偶联抑制剂的作用。我们认为，Na+的正电荷在导致偶联状态时模拟了类囊体腔中H+正电荷的功能。即使是更低浓度的Ca2+（二价阳离子）或Al3+（三价阳离子）也能发挥NaCl（单价阳离子）的功能。我们得出结论，NaCl作为偶联增强剂的这种功能不具有特异性，一般来说，在非偶联类囊体膜中引起偶联需要正电荷。
