Fig. 5.

Phosphorylation sites were identified by LC-MS/MS for BR-regulated proteins. Shown are tandem mass spectra obtained from precursor ions with m/z value 569.9506³⁺, 930.4570³⁺, and 667.9269⁵⁺ corresponding, respectively, to a peptide spanning residues Ala-501 to Arg-514 of TPR protein (At1g62740) phosphorylated at Thr507 (A), a double phosphorylated peptide (at Ser-62 and Thr-66) spanning the residues Lys-60 to Arg-84 of PCK1 (B), and a peptide (phosphorylated in Thr-122) spanning residues Lys-116 to Lys-147 of PCK1 (C). Phosphorylated residues are labeled in the peptide sequence with a “P” in superscript to their right side. The observed sequence ions are displayed. Phosphate losses are marked with circles in the sequence.