title: Binding of an extracellular steroid-binding globulin to membranes and soluble receptors from human breast cancer cells (MCF-7 cells).
abstract: Studies of MCF-7 breast cancer cells demonstrated that sex hormone-binding globulin (SHBG) is internalized by receptor-mediated endocytosis. The present study demonstrated specific binding of SHBG to receptor on membranes isolated from MCF-7 cells. Scatchard analysis of these binding studies suggested that SHBG binds to a single class of sites on membranes. The analysis yielded a dissociation constant (Kd) at 37 C of 3 x 10(-8) M and a binding capacity of 48 +2- 0.12 pmol/mg protein. A procedure for solubilizing the SHBG receptor from MCF-7 membranes used buffers containing protease inhibitors, 10% glycerol, and 10 mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. Solubilization of the receptor resulted in a 5-fold increase in its binding capacity (246 +/- 14 pmol/mg protein) and a 10-fold decrease in binding affinity (Kd at 37 C = 2 x 10(-7) M).
authors.affiliation: Population Council, New York, NY 10021.
authors.forename: C S
authors.initials: CS
authors.lastname: Porto
authors.forename: N A
authors.initials: NA
authors.lastname: Musto
authors.forename: C W
authors.initials: CW
authors.lastname: Bardin
authors.forename: G L
authors.initials: GL
authors.lastname: Gunsalus
mesh_terms: D001667:Binding, Competitive; D001943:Breast Neoplasms; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D012738:Sex Hormone-Binding Globulin; C063572:sex hormone-binding globulin receptor