Figure 2

GRP78 acetylation assessed inU251 cells treated with vorinostat (1 µM, 24 hours) and vehicle control using LC-MS/MS. The peptide was detected at 16.20 minutes in the total ion chromatogram (A) with a mass-to-charge ratio of 855.4332 (B). The tandem mass spectrum matched the sequence, (K)LGG_AcKLSSEDKET_OxMEK(A), indicating increased lysine-585 acetylation in vorinostat treated cells; the detection of y₁₁ and y₁₂ is consistent with this localization (C). The assignment was made with MASCOT with an ion score 35.8; SEQUEST XCorr 2.30 ΔC_n 0.15.