期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：4
页码：1675-1679
DOI：10.1073/pnas.75.4.1675
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Both insulin and human epidermal growth factor-urogastrone (EGF/URO) can be covalently linked to specific rat liver membrane binding sites by glutaraldehyde coupling followed by sodium borohydride reduction to yield affinity-labeled membrane constituents sufficiently stable for solubilization and further analysis by various techniques. Solubilization of membranes covalently labeled with 125I-labeled insulin yields a component with chromatographic properties identical to those of a soluble insulin receptor characterized in previous studies. A second soluble insulin-binding component that is not revealed by the affinity-labeling method and that has not yet been reported can also be detected. Membranes similarly labeled with 125I-labeled EGF/URO yield one major and two minor ligand-specific soluble (Triton X-100) affinity-labeled components, as detected by chromatography on Sepharose 6B. Further analysis of the EGF/URO-labeled components by affinity chromatography on concanavalin A-Sepharose, by disc gel electrophoresis, and by enzymatic digestion suggests that the major specific binding component for EGF/URO in liver membranes is a glycoprotein subunit of approximately 100,000 daltons that possesses a 20,000-dalton portion inaccessible to proteolytic cleavage when the subunit is anchored in the membrane. The affinity labeling approach described should prove of use for the study of other polypeptide receptors that, like the EGF/URO receptor, lose their ligand recognition property subsequent to membrane solubilization.
