Anti-N1-Phosphohistidine (1-pHis) Antibody, clone SC1-1 clone SC1-1, from rabbit

Phosphorylation plays an important role in regulating protein activities and various cellular signaling events in cells. Limited by the tools available for phosphohistidine (pHis) detection, the majority of studies focus on serine, threonine, and tyrosine phosphorylations. Histidine phosphorylation can occur at either N1 (1-pHis) or N3 (3-pHis) of the imidazole ring. The development of peptides containing stable phosphoryltriazolylalanine analogues of 1-pHis and 3-pHis (1-pTza and 3-pTza) allows the generation of antibodies for studying both histidine N1 and N3 phosphorylations in signaling events. There is growing evidence implicating His kinases in cancer and tumor metastasis and the first metastasis suppressor gene identified is one of the two known mammalian His kinases, Nm23-H1 (also known as NME1, nucleoside diphosphate kinase, or NDPK-A). Nm23-H1/NME1 and the closely related Nm23-H2 (NME2/NDPK-B) catalyze the transfer of phosphate from ATP onto Nucleoside-diphosphates (NDPs) through a 1-pHis enzyme intermediate. Nm23-H1/-H2 also possess His kinase activity, transferring the phosphate from the active site pHis onto a His in a target protein. Metabolic enzymes such as phosphoglycerate mutase (PGAM), succinyl CoA synthase (SCS), and ATP citrate lyase (ACL) also use pHis as an enzyme intermediate. Unlike NME1/2, PGAM uses 3-pHis as an enzyme intermediate. In addition to eukaryotes, histidine phosphorylation is well documented in bacterial "two-component" signaling pathways involved in chemotaxis, although the phosphate is transferred from the pHis formed in the receptor/sensor protein to Asp residues of an acceptor response regulator protein, and the receptor/sensor protein essentially functions as an aspartate kinase.