Affinity labeling of forskolin-binding proteins. Comparison between glucose carrier and adenylate cyclase.
An [125I]iodoazidosalicylic acid derivative of forskolin was synthesized for identification of the diterpene's binding sites on the catalytic subunit of adenylate cyclase and on glucose transport proteins. The affinity label was selectively incorporated into proteins of Mr 40,000-60,000 in membranes from human erythrocytes and from various other tissues. The iodoazidosalicylic acid derivative also specifically labeled the catalytic moiety of adenylate cyclase from rabbit myocardial membranes. However, the structural requirements of the two forskolin-binding sites must be different, since the affinity of the photolabel for the glucose carriers is much higher than that for the cyclase catalyst. Furthermore, the label is readily competed with by D-glucose and cytochalasin B for its binding site on the glucose carrier but not on adenylate cyclase.
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Department of Physiological Chemistry, University of Würzburg, Medical School, FRG.
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D000262:Adenylyl Cyclases / Q000032:analysis*; D000345:Affinity Labels / Q000138:chemical synthesis*; D000818:Animals; D001386:Azides / Q000138:chemical synthesis*; D001665:Binding Sites; D001667:Binding, Competitive; D002462:Cell Membrane / Q000201:enzymology; D005576:Colforsin / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D003571:Cytochalasin B / Q000032:analysis; D004224:Diterpenes; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000032:analysis; D005947:Glucose / Q000032:analysis; D006801:Humans; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D009206:Myocardium / Q000201:enzymology; D011817:Rabbits
D000345:Affinity Labels; D001386:Azides; D004224:Diterpenes; D009004:Monosaccharide Transport Proteins; C059841:3'-iodo-4'-azidosalicylamidoethylamido-7-succinyldeacetylforskolin; D005576:Colforsin; D003571:Cytochalasin B; D000262:Adenylyl Cyclases; D005947:Glucose