Photolabelling of the prostaglandin E sub(2) receptor in cardiac sarcolemmal vesicles

A ( super(3)H)azidophenacyl ester of PGE sub(2) (( super(3)H)azido-PGE sub(2)) was synthesized and used to photoaffinity label the protein component of the high affinity PGE sub(2) binding site in cardiac sarcolemma membrane. Photolysis of the isolated cardiac sarcolemmal vesicles in the presence of ( super(3)H)azido-PGE sub(2) resulted in the covalent labelling of a protein component that migrated on sodium dodecyl sulfate-polyacrylamide gels with an apparent molecular weight of 100,000. Incorporation of the ( super(3)H)azido-PGE sub(2) did not occur in the absence of photolysis. The results indicate that the 100-kDa photoaffinity labelled ( super(3)H)azido-PGE sub(2) binding protein contains the binding site for PGE sub(2) in isolated cardiac sarcolemma membranes.