The semiquinone at the Qi site of the bc1 complex explored using HYSCORE spectroscopy and specific isotopic labeling of ubiquinone in Rhodobacter sphaeroides via (13)C methionine and construction of a methionine auxotroph.

ABSTRACT: Specific isotopic labeling at the residue or substituent level extends the scope of different spectroscopic approaches to the atomistic level. Here we describe (13)C isotopic labeling of the methyl and methoxy ring substituents of ubiquinone, achieved through construction of a methionine auxotroph in Rhodobacter sphaeroides strain BC17 supplemented with l-methionine with the side chain methyl group (13)C-labeled. Two-dimensional electron spin echo envelope modulation (HYSCORE) was applied to study the (13)C methyl and methoxy hyperfine couplings in the semiquinone generated in situ at the Qi site of the bc1 complex in its membrane environment. The data were used to characterize the distribution of unpaired spin density and the conformations of the methoxy substituents based on density func

SUBMITTER: Hong S 

PROVIDER: S-EPMC4179594 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature