Identification and partial characterization of a retinal pigment epithelial membrane receptor for plasma retinol-binding protein.
We have developed a membrane binding assay by which we have been able to characterize the interaction between 125I-labeled retinol-binding protein and its receptor in microsome fractions derived from retinal pigment epithelial cells. The binding of retinol-binding protein to the membranes was fast, with a dissociation constant in the range of 31-72 nM, and maximum binding occurred at neutral pH. Receptor binding sites were also found in microsome fractions of liver and kidney, whereas lung and muscle contained few, if any. Chemical cross-linking of retinol-binding protein to the microsomal membranes yielded a major molecular complex of Mr 86,000 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein responsible for binding of retinol-binding protein was identified as a Mr 63,000 protein using a label transfer cross-linking technique. Further characterization demonstrated that the receptor for retinol-binding protein is a terminally glycosylated membrane protein noncovalently associated with a high molecular weight complex.
Båvik
C O
CO
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Eriksson
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U
Allen
R A
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Peterson
P A
PA
D001665:Binding Sites; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007120:Immunochemistry; D007668:Kidney / Q000737:chemistry; D007700:Kinetics; D008099:Liver / Q000737:chemistry; D008861:Microsomes / Q000737:chemistry; D010857:Pigment Epithelium of Eye / Q000737:chemistry* / Q000378:metabolism; D011233:Precipitin Tests; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000302:isolation & purification*; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D054839:Retinol-Binding Proteins, Plasma; D014018:Tissue Distribution
D003432:Cross-Linking Reagents; D011956:Receptors, Cell Surface; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma; C027928:retinol binding protein receptor