Slow dissociation of a charged ligand: analysis of the primary quinone Q(A) site of photosynthetic bacterial reaction centers.

ABSTRACT: Reaction centers (RCs) are integral membrane proteins that undergo a series of electron transfer reactions during the process of photosynthesis. In the Q(A) site of RCs from Rhodobacter sphaeroides, ubiquinone-10 is reduced, by a single electron transfer, to its semiquinone. The neutral quinone and anionic semiquinone have similar affinities, which is required for correct in situ reaction thermodynamics. A previous study showed that despite similar affinities, anionic quinones associate and dissociate from the Q(A) site at rates ≈10(4) times slower than neutral quinones indicating that anionic quinones encounter larger binding barriers (Madeo, J.; Gunner, M. R. Modeling binding kinetics at the Q(A) site in bacterial reaction centers. Biochemistry 2005, 44, 10994-11004). The present study i

SUBMITTER: Madeo J 

PROVIDER: S-EPMC3202297 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature