J binding protein (JBP) 1 and JBP2 catalyze the first step of base J biosynthesis: the hydroxylation of thymine in DNA to form 5-hydroxymethyluracil (hmU). Base J (beta-d-glucopyranosyloxymethyluracil) is a hyper-modified DNA base found in the DNA of kinetoplastids (Trypanosoma brucei, Trypanosoma cruzi, and Leishmania). JBP1 and JBP2 each contain a J-DNA binding domain and this oxygenase domain. They belong to the TET/JBP family of dioxygenases that require Fe2+ and alpha-ketoglutarate (also known as 2-oxoglutarate) for activity.
Jiyao W et al.(2023). "The conserved domain database in 2023.",