Properties of receptors for epidermal growth factor in detergent solution: evidence for heterogeneous aggregated states.
Between 60% and 100% of epidermal growth factor (EGF) binding activity was recovered from membranes of the A431 human epidermoid carcinoma cell line treated with solutions containing the nonionic detergent Triton X-100. Approximately half of the recovered binding activity was sedimented at low centrifugal force and hence was operationally insoluble in nonionic detergent solution. Receptors in both the detergent-soluble and -insoluble fractions displayed similar affinities for 125I-EGF, and the values were in good agreement with those obtained for receptors in untreated membranes. The receptors in both fractions also formed identical direct linkage complexes with 125I-EGF in similar yield, providing no evidence for partitioning of different molecular species of EGF receptors in the detergent-soluble membrane fraction of Sepharose 6-B revealed heterogeneity of 125I-EGF binding activity; the smallest and most monodisperse peak of activity resolved by this technique was eluted at a Strokes radius of 95 A. Operationally soluble 125I-EGF binding activity also behaved heterogeneously during velocity sedimentation; more than half the activity sedimented more rapidly than the apparently monidisperse, 7S form. An average of less than half the nonionic detergent-solubilized activity recovered from 10 independent membrane preparations behaved as an apparently monodisperse entity. Since a maximum of 60% of 125I-EGF binding activity was operationally soluble, less than 25% of the total EGF binding activity was recovered in an apparently monodisperse form. The remaining 75% of the EGF receptors displayed a marked tendency to exist as aggregates in nonionic detergent solutions.
D002294:Carcinoma, Squamous Cell / Q000032:analysis*; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D003902:Detergents; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors; D006801:Humans; D046911:Macromolecular Substances; D017830:Octoxynol; D011092:Polyethylene Glycols; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D012995:Solubility; D013501:Surface-Active Agents
D003902:Detergents; D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D013501:Surface-Active Agents; D011092:Polyethylene Glycols; D004815:Epidermal Growth Factor; D017830:Octoxynol; D066246:ErbB Receptors