Selective isolation of individual cell surface proteins from tissue culture cells by a cleavable biotin label

A method was developed to isolate cell surface proteins by a simple two-step procedure. Hepatocyte cell surface proteins were labeled by a cleavable biotin derivative in a covalent pulse reaction. Under the described conditions, NHS-SS-biotin proved to be an impermeant, cell surface-specific label which does not affect the impermeant, cell surface-specific label which does not affect the viability of rat hepatocytes. Biotinylated cell surface proteins could be selectively separated under non-denaturing conditions from non-biotinylated proteins and biotin-containing carboxylases by avidin affinity chromatography and sulfhydryl-mediated elution. Subsequent to alkylation of the eluted protein, individual cell surface proteins could be isolated by immunoprecipitation as shown for a selected Mr 120,000 glycoprotein gp120 of the hepatocyte plasma membrane. Using this technique, a transit time of gp120 from the endoplasmic reticulum to the cell surface of 2 h was determined. The results show that the combination of labeling with a cleavable biotin derivative, non-denaturing avidin affinity chromatography and immunoprecipitation is a useful method to isolate and study individual cell surface proteins.