Phosphorylated amino acid residues identified by mass spectrometry.

In vitro phosphorylated HNF4α was subjected to mass spectrometry analysis. The fragments containing the phosphorylated amino acid residues correspond to phosphorylation sites on the HNF4α protein. Detected phosphorylation sites (serine/threonine residues) in the cryptic fragments are marked bold and underlined. Affected phosphorylation sites appear in the DNA binding domain (DBD), the hinge, the ligand-binding domain (LBD) and the C-terminus of HNF4α, as well.