A vector that expresses secreted proteins on the cell surface.

A new vector, CDM8PI, has been constructed. It was derived from the plasmid expression vector CDM8, which has been used in the epitope-loss mutant isolation technique to map the epitopes on cell-surface proteins. The new vector allows the production of fusion proteins between normally secreted proteins and the membrane anchor moiety from a cell-surface protein, LFA-3, thereby expressing the fusion proteins on the cell surface. The vector extends the application of the epitope-loss mutant isolation technique to secreted proteins. The vector also allows the easy recovery of mutated proteins in unfused forms after the immunoselection and characterization.