The interaction of Tb³⁺ and La³⁺ cations with different photosystem II (PSII) membranes (intact PSII, Ca-depleted PSII (PSII[-Ca]) and Mn-depleted PSII (PSII[-Mn]) membranes) was studied. Although both lanthanide cations (Ln³⁺) interact only with Ca²⁺-binding site of oxygen-evolving complex (OEC) in PSII and PSII(-Ca) membranes, we found that in PSII(-Mn) membranes both Ln³⁺ ions tightly bind to another site localized on the oxidizing side of PSII. Binding of Ln³⁺ cations to this site is not protected by Ca²⁺ and is accompanied by very effective inhibition of Mn²⁺ oxidation at the high-affinity (HA) Mn-binding site ([Mn²⁺ + H₂O₂] couple was used as a donor of electrons). The values of the constant for inhibition of electron transport K_i are equal to 2.10 ± 0.03 µM for Tb³⁺ and 8.3 ± 0.4 µM for La³⁺, whereas OEC inhibition constant in the native PSII membranes is 323 ± 7 µM for Tb³⁺. The value of K_i for Tb³⁺ corresponds to K_i for Mn²⁺ cations in the reaction of diphenylcarbazide oxidation via HA site (1.5 µM) presented in the literature. Our results suggest that Ln³⁺ cations bind to the HA Mn-binding site in PSII(-Mn) membranes like Mn²⁺ or Fe²⁺ cations. Taking into account the fact that Mn²⁺ and Fe²⁺ cations bind to the HA site as trivalent cations after light-induced oxidation and the fact that Mn cation bound to the HA site (Mn4) is also in trivalent state, we can suggest that valency may be important for the interaction of Ln³⁺ with the HA site.

研究了 Tb ³⁺和 La ³⁺阳离子与不同光系统 II (PSII) 膜（完整的 PSII、Ca 耗尽的 PSII (PSII[-Ca]) 和 Mn 耗尽的 PSII (PSII[-Mn]) 膜）的相互作用. 尽管两种镧系元素阳离子 (Ln ³⁺ ) 仅与PSII 和 PSII(-Ca) 膜中的释氧复合物 (OEC) 的Ca ²⁺结合位点相互作用，但我们发现在 PSII(-Mn) 膜中，Ln ³⁺离子与位于 PSII 氧化侧的另一个位点紧密结合。LN的结合³⁺阳离子的网站不受保护的Ca ²⁺和伴随的Mn非常有效的抑制²⁺在高亲和力（HA）的Mn结合位点的氧化（[锰²⁺ + H ₂ O ₂ ] 对用作电子供体）。电子传递K _i抑制常数的值对于 Tb ³⁺等于 2.10 ± 0.03 µM，对于 La ³⁺为 8.3 ± 0.4 µM ，而天然 PSII 膜中的 OEC 抑制常数对于 Tb ³为 323 ± 7 µM ⁺。的值ķ_我为TB ³⁺相当于ķ_我为锰²⁺在经由HA的网站上的二苯卡巴肼氧化反应的阳离子（1.5μM）呈现在文献中。我们的结果表明 Ln ³⁺阳离子与 PSII(-Mn) 膜中的 HA Mn 结合位点结合，如 Mn ²⁺或 Fe ²⁺阳离子。考虑到 Mn ²⁺和 Fe ²⁺阳离子在光诱导氧化后作为三价阳离子结合到 HA 位点以及结合到 HA 位点 (Mn4) 的 Mn 阳离子也处于三价状态，我们可以建议该价态对于 Ln ³⁺与 HA 位点的相互作用可能很重要。