Abstract

The involvement of carbonic anhydrases (CA) and CA activity in the functioning of photosystem II (PSII) has been studied for a long time and has been shown in many works. However, so far only for CAH3 from Chlamydomonas reinhardtii there is evidence for its association with the donor side of PSII, where the CA activity of CAH3 can influence the functioning of the water-oxidizing complex (WOC). Our results suggest that CAH3 is also involved in the organization of the native structure of WOC independently of its CA activity. It was shown that in PSII preparations from wild type (WT) the high O₂-evolving activity of WOC was observed up to 100 mM NaCl in the medium and practically did not decrease with increasing incubation time with NaCl. At the same time, the WOC function in PSII preparations from CAH3-deficient mutant cia3 is significantly inhibited already at NaCl concentrations above 35 mM, reaching 50% at 100 mM NaCl and increased incubation time. It is suggested that the absence of CAH3 in PSII from cia3 causes disruption of the native structure of WOC, allowing more pronounced conformational changes of its proteins and, consequently, suppression of the WOC active center function, when the ionic strength of the medium is increased. The results of Western blot analysis indicate a more difficult removal of PsbP protein from PSII of cia3 at higher NaCl concentrations, apparently due to the changes in the intermolecular interactions between proteins of WOC in the absence of CAH3. At the same time, the values of the maximum quantum yield of PSII did not practically differ between preparations from WT and cia3, indicating no effect of CAH3 on the photoinduced electron transfer in the reaction center of PSII. The obtained results indicate the involvement of the CAH3 protein in the native organization of the WOC and, as a consequence, in the stabilization of its functional state in PSII from C. reinhardtii.

中文翻译：

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碳酸酐酶 CAH3 参与莱茵衣藻光系统 II 水氧化复合物的结构和功能稳定

摘要

碳酸酐酶 (CA) 和 CA 活性在光系统 II (PSII) 功能中的参与已被研究了很长时间，并已在许多作品中得到证明。然而，到目前为止，只有来自莱茵衣藻的CAH3有证据表明它与 PSII 的供体侧相关，其中 CAH3 的 CA 活性可以影响水氧化复合物 (WOC) 的功能。我们的结果表明 CAH3 还参与了 WOC 的天然结构的组织，而与其 CA 活动无关。结果表明，在来自野生型 (WT) 的 PSII 制剂中，高 O ₂- 在培养基中观察到 WOC 的进化活性高达 100 mM NaCl，并且实际上不会随着与 NaCl 的孵育时间的增加而降低。同时，来自 CAH3 缺陷突变体cia3 的PSII 制剂中的 WOC 功能在NaCl 浓度高于 35 mM 时已被显着抑制，在 100 mM NaCl 时达到 50%，并且孵育时间增加。这表明 cia3 的 PSII 中CAH3 的缺失导致 WOC 的天然结构的破坏，使其蛋白质的构象发生更明显的变化，因此，当介质的离子强度增加时，WOC 活性中心功能的抑制. 蛋白质印迹分析的结果表明从cia3 的PSII 中去除 PsbP 蛋白更困难在较高的 NaCl 浓度下，显然是由于在没有 CAH3 的情况下 WOC 蛋白质之间的分子间相互作用发生了变化。同时，PSII 的最大量子产率值在 WT 和cia3制备之间实际上没有差异，表明 CAH3 对 PSII 反应中心的光致电子转移没有影响。获得的结果表明 CAH3 蛋白参与了 WOC 的天然组织，因此，它在来自莱茵衣藻的PSII 中的功能状态稳定。