Comparison of in vivo and in vitro phosphorylation of the exocytosis-sensitive protein PP63/parafusin by differential MALDI mass spectrometric peptide mapping

Researchers have conducted experiments on phosphorylation sites in 63 kDa phosphoprotein PP63/parafusin of the ciliated protozoan Paramecium tetraurelia. The protein PP63/pf was found to be concentrated in the cell cortex of the specimen organism. It is highly probable that PP63/pf may be involved in the regulation of the exo- and endocytosis cycle due to its rapid occurence upon phosphorylation of PP63/pf-1. In vitro phosphorylation of recombinant PP63/pf was made possible through mass spectrometric peptide mapping.