Rhodopsin Forms a Dimer with Cytoplasmic Helix 8 Contacts in Native Membranes

Abstract

G protein-coupled receptors form dimers and higher-order oligomers in membranes, but the precise mode of receptor–receptor interaction remains unknown. To probe the intradimeric proximity of helix 8 (H8), we conducted chemical cross-linking of endogenous cysteines in rhodopsin in disk membranes. We identified a Cys316–Cys316 cross-link using partial proteolysis and liquid chromatography with mass spectrometry. These results show that a symmetric dimer interface mediated by H1 and H8 contacts is present in native membranes