Proton transfer pathway from the oxygen-evolving complex in photosystem II substantiated by extensive mutagenesis

Hiroshi Kuroda, Keisuke Kawashima, Kazuyo Ueda, Takuya Ikeda, Keisuke Saito, Ryo Ninomiya, Chisato Hida, Yuichiro Takahashi, Hiroshi Ishikita


29 被引用数 (Scopus)


We report a structure-based biological approach to identify the proton-transfer pathway in photosystem II. First, molecular dynamics (MD) simulations were conducted to analyze the H-bond network that may serve as a Grotthuss-like proton conduit. MD simulations show that D1-Asp61, the H-bond acceptor of H2O at the Mn4CaO5 cluster (W1), forms an H-bond via one water molecule with D1-Glu65 but not with D2-Glu312. Then, D1-Asp61, D1-Glu65, D2-Glu312, and the adjacent residues, D1-Arg334, D2-Glu302, and D2-Glu323, were thoroughly mutated to the other 19 residues, i.e., 114 Chlamydomonas chloroplast mutant cells were generated. Mutation of D1-Asp61 was most crucial. Only the D61E and D61C cells grew photoautotrophically and exhibit O2-evolving activity. Mutations of D2-Glu312 were less crucial to photosynthetic growth than mutations of D1-Glu65. Quantum mechanical/molecular mechanical calculations indicated that in the PSII crystal structure, the proton is predominantly localized at D1-Glu65 along the H-bond with D2-Glu312, i.e., pKa(D1-Glu65) > pKa(D2-Glu312). The potential-energy profile shows that the release of the proton from D1-Glu65 leads to the formation of the two short H-bonds between D1-Asp61 and D1-Glu65, which facilitates downhill proton transfer along the Grotthuss-like proton conduit in the S2 to S3 transition. It seems possible that D1-Glu65 is involved in the dominant pathway that proceeds from W1 via D1-Asp61 toward the thylakoid lumen, whereas D2-Glu312 and D1-Arg334 may be involved in alternative pathways in some mutants.

ジャーナルBiochimica et Biophysica Acta - Bioenergetics
出版ステータスPublished - 1月 1 2021

ASJC Scopus subject areas

  • 生物理学
  • 生化学
  • 細胞生物学


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