Abstract: Methods are provided for studying protein-protein interactions which require posttranslational modification of one of the proteins. The interaction is detected by reconstituting the activity of a transcriptional activator. This activity is dependent on the interactions between three different proteins. These include two chimeric proteins, one of which must be posttranslationally modified by the activity of the third protein in order for the chimeric proteins to interact. One of the chimeric proteins contains a transcriptional activation domain fused to a test protein. The second chimeric protein contains a DNA-binding domain of a transcriptional activator fused to the other test protein.

Abstract: The present invention involves the protein glycosyl-phosphatidyl-specific phospholipase D (GPI-PLD) in a substantially pure form, an isolated nucleotide sequence encoding GPI-PLD, vectors containing the isolated nucleotide sequence encoding GPI-PLD, and cells transformed by a vector containing the isolated nucleotide sequence encoding GPI-PLD, also nucleotide sequences, vectors and cells comprising hybrid genes with GPI-PLD, and methods for producing secreted proteins.