Quantification of proteasome subunits by mass spectroscopy in IP-deficient mice.

20S proteasomes were isolated from murine hearts from control mice and at day 4 and 8 p.i. from β5i/LMP7+/+ and β5i/LMP7-/- mice. The mixture of tryptic 20S proteasome peptides was separated prior to mass spectrometric analysis by reverse phase nano HPLC using a Proxeon System; MS-data were generated on an Orbitrap-MS equipped with a nanoelectrospray ion source as described in material and methods. MS ion intensities are shown for individual proteasome subunits as ratios between β5i/LMP7+/+ and β5i/LMP7-/- mice. Data are mean±SD from two technical replicates that have been performed each with two independent biological replicates. p