Matrix-assisted laser desorption ionization/quadrupole ion trap mass spectrometry of peptides. Application to the localization of phosphorylation sites on the P protein from Sendai virus.

The polymerase-associated phosphoprotein (P protein) from Sendai virus, a murine Paramyxovirus, is reported in the literature to be a highly phosphorylated protein. In vitro studies have detected phosphorylation in different regions of the protein, while a single phosphopeptide (identified as the sole phosphorylation) site) was observed using in vivo techniques. In this work, two phosphorylation sites of the P protein from Sendai virus are localized by a direct approach using matrix-assisted laser desorption ionization/quadrupole ion trap mass spectrometry. A computer-aided approach is used to confirm peptide identification.