Light induced EPR spectra of reaction centers from Rhodobacter sphaeroides at 80K: Evidence for reduction of Q(B) by B-branch electron transfer in native reaction centers.

ABSTRACT: Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides capture solar energy by electron transfer from primary donor, D, to quinone acceptor, Q(B,) through the active A-branch of electron acceptors, but not the inactive B-branch. The light induced EPR spectrum from native RCs that had Fe(2+) replaced by Zn(2+) was investigated at cryogenic temperature (80K, 35 GHz). In addition to the light induced signal due to formation of D(+•)Q(A) (-•) observed previously, a small fraction (~5%) of the signal displayed very different characteristics: (1) The signal was absent in RCs in which the Q(B) was displaced by the inhibitor stigmatellin. (2) Its decay time (τ=6 s) was the same as observed for D(+•)Q(B) (-•) in mutant RCs lacking Q(A,) which is significantly slower than for D(+•)Q(A) (

SUBMITTER: Paddock ML 

PROVIDER: S-EPMC2156152 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature