Photoaffinity labeling of the K+-channel-associated apamin-binding molecule in smooth muscle, liver and heart membranes.
High-affinity binding sites for mono[125I]iodoapamin were detected in membranes (Kd = 59 pM, Bmax = 24 fmol/mg protein) and cultured cells (Kd = 69 pM, Bmax = 2.8 fmol/mg protein) from rat heart and in membranes from guinea-pig ileum (Kd = 67 pM, Bmax 42 fmol/mg protein) and liver (Kd = 15 pM, Bmax = 43 fmol/mg protein). Binding was stimulated by K+ ions (K0.5 = 0.3-0.5 mM). Covalent labeling with arylazide [125I]iodoapamin derivatives showed that smooth muscle, liver and heart binding molecules are associated with a 85-87-kDa polypeptide. A second strongly labeled 57-kDa component was identified in liver membranes only.
D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D001030:Apamin / Q000031:analogs & derivatives / Q000378:metabolism*; D001386:Azides / Q000378:metabolism*; D001514:Bee Venoms / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000302:isolation & purification / Q000378:metabolism*
D000345:Affinity Labels; D001386:Azides; D001514:Bee Venoms; D007473:Ion Channels; D015221:Potassium Channels; D017981:Receptors, Neurotransmitter; C033799:apamin receptor; D001030:Apamin; C044789:4-azido-2-nitrophenylaminoacetylmonoiodoapamin; D011188:Potassium