PNNL

Abstract

Liquid chromatography-mass spectrometry (LC-MS) based approach for monitoring time dependent changes in the degree of nitration and oxidation of intact calmodulin (CaM) has been used to resolve approximately 500 CaM oxiforms. Tentative identifications of posttranslational modifications (PTMs) such as oxidation or nitration have been assigned by combining tryptic peptide information (generated from bottom-up analyses) with online collision induced dissociation (CID) tandem mass spectrometry (MS/MS) at the intact protein level. The reduction in abundance and diversity of oxidatively modified CaM (i.e. nitrated tyrosines and oxidized methionines) induced by macrophage activation has been explored and semi-quantified for different oxidation degrees of CaM (i.e. no oxidation, moderate and high oxidation). This work demonstrates the power of top-down approach to identify hundreds of combinations of posttranslational modifications (PTMs) for single protein target such as CaM.