5. Ser, Thr, and Tyr are well known targets for
post-translational phosphorylation. A lesser known target is His
[Kee and Muir, ACS Chem. Biol., 2012, 7 (1), pp 44–51],
which can be phosphorylated at either the N-1 or N-3 positions of
the imidazole group. One hindrance in studying this phosphorylation
is its chemical lability, especially at low pH. Nevertheless, His
phosphorylation is now recognized as an important signaling
mechanism in prokaryotes and lower eukaryotes, and is being
associated with mammalian...