Boussac A, Zimmermann J L, Rutherford A W
Service de Bioénergétique (URA CNRS 1290), Département de Biologie Cellulaire et Moléculaire, CEN Saclay, Gif-sur-Yvette, France.
FEBS Lett. 1990 Dec 17;277(1-2):69-74. doi: 10.1016/0014-5793(90)80811-v.
NaCl/EGTA-washing of photosystem II (PS-II) results in the removal of Ca2+ and the inhibition of oxygen evolution. Two new EPR signals were observed in such samples: a stable and modified S2 multiline signal and an S3 signal [(1989) Biochemistry 28, 8984-8989]. Here, we report what factors are responsible for the modifications of the S2 signal and the observation of the S3 signal. The following results were obtained. (i) The stable, modified, S2 multiline signal can be induced by the addition of high concentrations of EGTA or citrate to PS-II membranes which are already inhibited by Ca(2+)-depletion. (ii) The carboxylic acids act in the S3-state, are much less effective in S2 and have no effect in the S1-state. (iii) The extrinsic polypeptides (17- and 23-kDa) are not required to observe either the modified S2 signal or the S3 signal. However, they do influence the splitting and the lifetime of the S3 signal, and they seem to have a slight influence on the hyperfine pattern of the S2 signal. (iv) The S3 signal can be observed in Ca(2+)-depleted PS-II which does not exhibit the modified multiline signal. Then, it is proposed that formation of histidine radical during the S2 to S3 transition in Ca(2+)-depleted PS-II [(1990) Nature 347, 303-306] also occurs in functional PS-II.
用NaCl/EGTA洗涤光系统II（PS-II）会导致Ca2+的去除以及氧气释放的抑制。在这类样品中观察到了两种新的电子顺磁共振（EPR）信号：一种稳定且经过修饰的S2多线信号和一种S3信号[（1989年）《生物化学》28卷，8984 - 8989页]。在此，我们报告了导致S2信号修饰和S3信号出现的因素。得到了以下结果。（i）向已经因Ca2+耗竭而受到抑制的PS-II膜中添加高浓度的EGTA或柠檬酸盐，可诱导出稳定、经过修饰的S2多线信号。（ii）羧酸在S3状态下起作用，在S2状态下效果要差得多，而在S1状态下没有作用。（iii）观察修饰后的S2信号或S3信号并不需要外在多肽（17 kDa和23 kDa）。然而，它们确实会影响S3信号的分裂和寿命，并且似乎对S2信号的超精细图谱有轻微影响。（iv）在不呈现修饰后的多线信号的Ca2+耗竭的PS-II中可以观察到S3信号。因此，有人提出在功能正常的PS-II中，在Ca2+耗竭的PS-II从S2向S3转变过程中组氨酸自由基的形成[（1990年）《自然》347卷，303 - 306页]也会发生。
