Photogenerated reagents for membranes: selective labeling of intrinsic membrane proteins in the human erythrocyte membrane.

1-[3H]Spiro[adamantane-4,4'-diazirine], a lipophilic, photoactivatable reagent designed to label those segments of intrinsic proteins that lie within the lipid bilayer of biological membranes, has been evaluated. The reagent labels the intrinsic proteins of human erythrocyte membranes far more heavily than it labels the extrinsic proteins. This result, together with a detailed analysis of the label distribution in several well-characterized membrane proteins [Goldman, D.W., Pober, J.S., White, J., & Bayley, H. (1979) Nature (London) 280, 841], demonstrates that labeling with adamantanediazirine is a convenient and rapid method both for distinguishing intrinsic from extrinsic membrane proteins and for locating within intrinsic proteins those amino acid residues that are in contact with the hydrocarbon core of the lipid bilayer.