The plastoquinol–plastoquinone exchange mechanism in photosystem II: insight from molecular dynamics simulations

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• 作者：Veranika Zobnina ; Maya D. Lambreva ; Giuseppina Rea…
• 关键词：Photosystem II ; plastoquinone ; Plastoquinol ; Protein dynamics ; Molecular dynamics simulations ; Plastoquinol release mechanism
• 刊名：Photosynthesis Research
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：131
• 期：1
• 页码：15-30
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Plant Sciences; Plant Physiology; Biochemistry, general; Plant Genetics & Genomics;
• 出版者：Springer Netherlands
• ISSN：1573-5079
• 卷排序：131

文摘

In the photosystem II (PSII) of oxygenic photosynthetic organisms, the reaction center (RC) core mediates the light-induced electron transfer leading to water splitting and production of reduced plastoquinone molecules. The reduction of plastoquinone to plastoquinol lowers PSII affinity for the latter and leads to its release. However, little is known about the role of protein dynamics in this process. Here, molecular dynamics simulations of the complete PSII complex embedded in a lipid bilayer have been used to investigate the plastoquinol release mechanism. A distinct dynamic behavior of PSII in the presence of plastoquinol is observed which, coupled to changes in charge distribution and electrostatic interactions, causes disruption of the interactions seen in the PSII–plastoquinone complex and leads to the “squeezing out” of plastoquinol from the binding pocket. Displacement of plastoquinol closes the second water channel, recently described in a 2.9 Å resolution PSII structure (Guskov et al. in Nat Struct Mol Biol 16:334–342, 2009), allowing to rule out the proposed “alternating” mechanism of plastoquinol–plastoquinone exchange, while giving support to the “single-channel” one. The performed simulations indicated a pivotal role of D₁-Ser264 in modulating the dynamics of the plastoquinone binding pocket and plastoquinol–plastoquinone exchange via its interaction with D₁-His252 residue. The effects of the disruption of this hydrogen bond network on the PSII redox reactions were experimentally assessed in the D₁ site-directed mutant Ser264Lys.