Energetics of tryptophan residues in electron transfer and photoprotection of type-II photosynthetic reaction centers.

ABSTRACT: Tryptophan is the strongest UV chromophore in proteins, and its biosynthesis is the most energy-consuming among all amino acids. In the transmembrane region of purple bacterial photosynthetic reaction centers (PbRC), tryptophan residues are densely concentrated near the inactive electron-transfer branch in subunit M, forming part of the carotenoid binding site. We investigated the redox potentials (E _m) of tryptophan residues in PbRC and O₂-evolving photosystem II (PSII) by solving the linear Poisson-Boltzmann equation, considering equilibrium with all titratable sites in the entire protein. The tryptophan mediating superexchange electron transfer between the active (bacterio)pheophytin and primary quinone exhibits the highest E _m value in bot

SUBMITTER: Noji T 

PROVIDER: S-EPMC12445680 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature