van Vliet P, Boussac A, Rutherford A W
Section de Bioénergétique (URA CNRS 1290), Département de Biologie Cellulaire et Moléculaire, CEA Saclay, Gif-sur-Yvette, France.
Biochemistry. 1994 Nov 8;33(44):12998-3004. doi: 10.1021/bi00248a008.
The effects of Cl-depletion in photosystem II (PS-II)-enriched membranes have been investigated by electron paramagnetic resonance (EPR) spectroscopy after removal of the 17- and 23-kDa polypeptides and depletion of Ca2+ by NaCl treatment. When the salt treatment was done in the presence of a high concentration (5 mM) of the chelator [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA), a modified dark-stable multiline signal was observed from the S2 state and a 13 mT wide S3 signal could be generated by illumination at 0 degrees C as reported previously for experiments conducted under these conditions [Boussac, A., Zimmermann, J.-L., & Rutherford, A. W. (1990) FEBS Lett. 277, 69-74]. The modified S2 multiline signal was lost after a further Cl- depletion in the presence of a low EGTA concentration (50 microM). Upon Cl- reconstitution, a normal S2 multiline signal could be generated by continuous illumination at 200 K. In contrast, a lowering of the EGTA concentration (50 microM) alone, in the presence of Cl- (30 mM), had no effect on the modified S2 multiline signal. These results indicate that the modification of S2 is due to binding of the chelator to PS-II and that Cl- stabilizes the chelator binding. When Cl- depletion in Ca(2+)-depleted PS-II was done in the presence of a high concentration of EGTA (5 mM), the modified S2 multiline signal disappeared but was regenerated by Cl- reconstitution in darkness. These results indicate that when Cl- depletion is done to the EGTA-modified PS-II, the S2 multiline signal disappears but the S2 state remains stable in the dark.(ABSTRACT TRUNCATED AT 250 WORDS)
在去除17 kDa和23 kDa多肽并通过NaCl处理耗尽Ca2+后，利用电子顺磁共振（EPR）光谱研究了富含光系统II（PS-II）的膜中Cl耗尽的影响。如先前在这些条件下进行的实验所报道的那样[Boussac, A., Zimmermann, J.-L., & Rutherford, A. W. (1990) FEBS Lett. 277, 69 - 74]，当在高浓度（5 mM）螯合剂[乙二胺双（氧乙烯腈）]四乙酸（EGTA）存在下进行盐处理时，从S2状态观察到一种修饰的暗稳定多线信号，并且在0℃光照下可产生13 mT宽的S3信号。在低EGTA浓度（50 μM）存在下进一步耗尽Cl后，修饰的S2多线信号消失。Cl重构后，在200 K连续光照下可产生正常的S2多线信号（ABSTRACT TRUNCATED AT 250 WORDS）。相反，在Cl（30 mM）存在下单独降低EGTA浓度（50 μM）对修饰的S2多线信号没有影响。这些结果表明，S2的修饰是由于螯合剂与PS-II结合所致，并且Cl稳定了螯合剂的结合。当在高浓度EGTA（5 mM）存在下对Ca(2+)耗尽的PS-II进行Cl耗尽时，修饰的S2多线信号消失，但在黑暗中通过Cl重构可使其再生。这些结果表明，当对EGTA修饰过的PS-II进行Cl耗尽时，S2多线信号消失，但S2状态在黑暗中保持稳定。
