An expression vector, pLEF, has been used to produce the intracellular
domain (IC) of the human CD95 (Fas/APO-1) apoptosis receptor as a glu
tathione S-transferase (GST) fusion protein in murine L929 fibroblasts
. GST::CD95IC was affinity-purified in a single step using glutathione
-Sepharose. Purification of GST::CD95IC from P-32-labelled L999 cells
and cleavage with thrombin revealed that CD95IC was phosphorylated in
vivo when produced as a GST fusion protein. Therefore, pLEF may facili
tate the mapping of in vivo-modified sites of eukaryotic proteins.