Open AccessPhotoaffinity labeling of the K + ‐channel‐associated apamin‐binding molecule in smooth muscle, liver and heart membranes
Author(s) -
MARQUÈZE Beatrice,
SEAGAR Michael J.,
COURAUD François
Publication year - 1987
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1987.tb13611.x
Subject(s) - membrane , apamin , guinea pig , photoaffinity labeling , binding site , chemistry , biochemistry , covalent bond , binding protein , microbiology and biotechnology , biology , biophysics , endocrinology , potassium channel , organic chemistry , gene
High‐affinity binding sites for mono[ 125 I]iodoapamin were detected in membranes ( K d = 59 pM, B max = 24 fmol/mg protein) and cultured cells ( K d = 69 pM, B max = 2.8 fmol/mg protein) from rat heart and in membranes from guinea‐pig ileum ( K d = 67 pM, B max = 42 fmol/mg protein) and liver ( K d = 15 pM, B max = 43 fmol/mg protein). Binding was stimulated by K + ions ( K 0.5 = 0.3 – 0.5 mM). Covalent labeling with arylazide [ 125 I]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.