Fig 1: NPM is expressed in B16F1 cells and can be citrullinated in vitro. Immunoblot (A) of lysates from B16F1 (lane 1), ladder (lane 2), recombinant NPM protein (lane 3) probed for NPM and ß actin. The expected size for NPM (35 kDa) and ß-actin (42 kDa) is shown. In vitro citrullination of recombinant NPM protein was performed in the presence of either (B) PAD2 or (C) PAD4, followed by mass spectrometry analysis to identify the sites of citrullination. NPM, nucleophosmin.