Stigmatellin probes the electrostatic potential in the QB site of the photosynthetic reaction center.

ABSTRACT: The electrostatic potential in the secondary quinone (QB) binding site of the reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides determines the rate and free energy change (driving force) of electron transfer to QB. It is controlled by the ionization states of residues in a strongly interacting cluster around the QB site. Reduction of the QB induces change of the ionization states of residues and binding of protons from the bulk. Stigmatellin, an inhibitor of the mitochondrial and photosynthetic respiratory chain, has been proven to be a unique voltage probe of the QB binding pocket. It binds to the QB site with high affinity, and the pK value of its phenolic group monitors the local electrostatic potential with high sensitivity. Investigations with different type

SUBMITTER: Gerencser L 

PROVIDER: S-EPMC4302209 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature