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Solubilization of complexes between tumor-associated and H-2 antigens from a tumor cell plasma membrane
The tumor-associated cell surface antigens (TAA) gp 71 and AgI cocap H-2, but are not associated with H-2 following solubilization of membrane with detergent. We have attempted to solubilize intact TAA/H-2 complexes from surface-labeled L cells using decreasing concentrations of the nonionic detergent Nonidet-P 40 (NP 40). Associations between gp 71 and H-2 and between AgI and H-2 in solution were detected using sequential immunoprecipitation. gp 71/H-2 and AgI/H-2 complexes were solubilized at the lowest detergent concentration used, 0.01% NP 40. No coprecipitation of these antigen pairs was seen at any higher NP 40 concentration tested. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed lthat precipitation of antigens solulbilized in 0.01% NP 40 leads to coprecipitation of a small number of other protein peaks and does not appear to involve wholesale inclusion of labeled membrane proteins. These results, together with previous observations of cocapping between TAA and H-2 antigens, suggest that the molecules are associated with one another in the membrane. Detergent solubilization of membranes with all but the most gentle conditions leads to disruption of these complexes.
The tumor-associated cell surface antigens (TAA) gp 71 and AgI cocap H-2, but are not associated with H-2 following solubilization of membrane with detergent. We have attempted to solubilize intact TAA/H-2 complexes from surface-labeled L cells using decreasing concentrations of the nonionic detergent Nonidet-P 40 (NP 40). Associations between gp 71 and H-2 and between AgI and H-2 in solution were detected using sequential immunoprecipitation. gp 71/H-2 and AgI/H-2 complexes were solubilized at the lowest detergent concentration used, 0.01% NP 40. No coprecipitation of these antigen pairs was seen at any higher NP 40 concentration tested. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed lthat precipitation of antigens solulbilized in 0.01% NP 40 leads to coprecipitation of a small number of other protein peaks and does not appear to involve wholesale inclusion of labeled membrane proteins. These results, together with previous observations of cocapping between TAA and H-2 antigens, suggest that the molecules are associated with one another in the membrane. Detergent solubilization of membranes with all but the most gentle conditions leads to disruption of these complexes.