Effect of lanthanides on oxidation of Mn 2+ cations via a high-affinity Mn-binding site in photosystem II membranes

• Published in: Journal of inorganic biochemistry 2023-07, Vol.244, p.112237
• Main Authors: Lovyagina, E R, Luneva, O G, Loktyushkin, A V, Semin, B K
• Format: Article
• Language: English
• Subjects: Binding Sites; Calcium - metabolism; Cations; Electron Transport; Oxidation-Reduction; Oxygen - metabolism; Photosystem II Protein Complex - chemistry
• ISSN: 1873-3344
• DOI: 10.1016/j.jinorgbio.2023.112237

Lanthanide cations (La and Tb ) bind to the Ca-binding site of the oxygen-evolving complex in Ca-depleted PSII membranes and irreversibly inhibit the oxygen evolution. Оn the other hand, EPR measurement of Mn concentration in buffer revealed that lanthanide cations inhibit the light-dependent oxidation of Mn cations via the high-affinity Mn-binding site in Mn-depleted PSII membranes, which suggests that they bind to and inhibit the high-affinity Mn-binding site of the oxygen-evolving complex. The inhibition is irreversible, bound Ln cation could not be washed out from the sample. Calcium ion inhibits oxidation of Mn (5 μM) at very high concentration (tens mM) and the inhibition is reversible. In this work we measured the reduction rate of exogenic electron acceptor 2,6-dichlorophenolindophenol during the oxidation of Mn cations in the Ca-depleted PSII and in the Ca-depleted PSII treated with lanthanides after extraction of Mn cluster from these preparations. We found that irreversible binding of the lanthanide cation to the Ca-binding site in the Ca-depleted PSII membranes leads to a partial inhibition of the high-affinity Mn-binding site.