Controlling electron transfer between the two cofactor chains of photosystem I by the redox state of one of their components.

ABSTRACT: Two functional electron transfer (ET) chains, related by a pseudo-C2 symmetry, are present in the reaction center of photosystem I (PSI). Due to slight differences in the environment around the cofactors of the two branches, there are differences in both the kinetics of ET and the proportion of ET that occurs on the two branches. The strongest evidence that this is indeed the case relied on the observation that the oxidation rates of the reduced phylloquinone (PhQ) cofactor differ by an order of magnitude. Site-directed mutagenesis of residues involved in the respective PhQ-binding sites resulted in a specific alteration of the rates of semiquinone oxidation. Here, we show that the PsaA-F689N mutation results in an ∼100-fold decrease in the observed rate of PhQA(-) oxidation. This is the l

SUBMITTER: Santabarbara S 

PROVIDER: S-EPMC4375535 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature