Molecular origin of electron paramagnetic resonance line shapes on β-barrel membrane proteins: the local solvation environment modulates spin-label configuration.

ABSTRACT: In this work, electron paramagnetic resonance (EPR) spectroscopy and X-ray crystallography were used to examine the origins of EPR line shapes from spin-labels at the protein-lipid interface on the β-barrel membrane protein BtuB. Two atomic-resolution structures were obtained for the methanethiosulfonate spin-label derivatized to cysteines on the membrane-facing surface of BtuB. At one of these sites, position 156, the label side chain resides in a pocket formed by neighboring residues; however, it extends from the protein surface and yields a single-component EPR spectrum in the crystal that results primarily from fast rotation about the fourth and fifth bonds linking the spin-label to the protein backbone. In lipid bilayers, site 156 yields a multicomponent spectrum resulting from differ

SUBMITTER: Freed DM 

PROVIDER: S-EPMC3199607 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature