The Interaction of the Membrane Binding Segment of Cytochrome B5with Phospholipid Vesicles. A Pulse-radiolysis Investigation

Abstract

The reactions of the radical anions Br2- and (SCN)2- produced by pulse-radiolysis have been used to study the interaction of dipalmitoyl phosphatidyl choline vesicles with the membrane binding segment (MBS) of cytochrome b5. Tryptophan oxidation by Br2- at neutral pH was characterized spectrophotometrically in detergent-solubilized solutions of MBS; the attack of tyrosine by (SCN)2- under alkaline conditions could also be observed directly. The incorporation of MBS into the lipid bilayer protected the tryptophan, tyrosine and methionine residues from oxidation by Br2- or (SCN)2-. Some structural implications of these results are discussed.