Figure 3
From: Phosphorylation regulates human T-cell leukemia virus type 1 Rex function
Mapping Rex-1 phosphorylation sites by mass spectrometry. (A) A compilation of the results obtained with LC-MS/MS analysis of S-tagged Rex-1. The 189 aa Rex-1 protein is depicted with phosphorylation sites identified (*). The table (inset) shows % total amino acid coverage from LC-MS/MS analysis. (B) A representative MS/MS spectrum of the tryptic phosphopeptide, which identified phosphorylation at Thr-174 is shown. CID Mass spectrum of m/z 1020.42 (3+) revealed a 29 aa peptide of Mr 3058.23. B and Y ion designations marked with (0) indicate a loss of H2O are doubly charged. The presence of the b10, b11 and b12 ions maps the phosphorylation to Thr-174. The MASCOT peptide score was 82 with an expected score of 0.0028.