FIG. 2.
Surface expression of mutant glycoproteins in COS-1 cells. Surface biotinylation was used to label envelope glycoproteins on transiently transfected cells. (A) Total glycoprotein was immunoprecipitated from lysates of metabolically labeled cells. Three quarters of the immunoprecipitate was further subjected to precipitation with streptavidin reagents to recover that portion of the Env present on the cell surface. WT, wild type; mock, mock transfected. (B) The ratio of surface to total glycoprotein (gp120) was calculated from panel A using phosphorimaging analysis as described in Materials and Methods. Data for the mutants are presented relative to the wild-type ratio. Representative analyses are shown for panels A and B.