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.

Selectively detects proteins with histidine(s) phosphorylated at N1 of the imidazole ring (1-pHis), but not 3-pHis.

Target modification is not species specific.

Epitope: N1-phosphohistidine (1-pHis)

KLH-conjugated library of random peptides containing non-hydrolyzable phosphohistidine analogue 1-pTza.

Anti-N1-Phosphohistidine (1-pHis) antibody, clone SC50-3 is an isomer-specific monoclonal Ab to specifically detect histidine phosphorylated at position N1. This purified mAb is backed by published data demonstrating performance in Western blotting and dot blot applications.

Dot Blot Analysis: A representative lot detected peptides containing 1-pTza, but not 3-pTza phosphohistidine analogue. Clone SC50-3 displayed no immunoreactivity toward peptides containing only phosphorylated tyrosine or non-phosphorylated histidine (Fuhs, S.R., et al. (2015). Cell. 162(1):198-210).

Western Blotting Analysis: Clone SC50-3 hybridoma culture supernatant was employed for Western blotting analysis of heat-sensitive histidine N1-phosphorylation (1-pHis) of exogenously expressed NM23-H1/NME1 fusion proteins in lysates from transformed E. coli and HEK293 transfectants (Fuhs, S.R., et al. (2015). Cell. 162(1):198-210).

Note: DO NOT HEAT SAMPLES prior to phosphohistidine detection. Histidine phosphorylation is heat and acid labile. To generate negative control for specificity test, an aliquot of sample can be heated at 95ºC for 10-15 minutes to reverse histidine phosphorylation. Alternatively, an aliquot of sample can be incubated under acidified pH at 37ºC for 15 minutes to reduce histidine phosphorylation. Acidify each 100 µL sample with 25 µL of 1 M HCl before the incubation, then neutralize with 25 µL of 1 M NaOH prior to phosphohistidine detection.

Evaluated by Western Blotting of NME1 autophosphorylation reaction.

Western Blotting Analysis: 0.24 µg/mL of this antibody detected recombinant human NME1 (NM23-H1) with N1-phosphohistidine (1-pHis) in a 5 µg aliquot of autophosphorylation reaction.

Variable depending on the histidine-phosphorylated proteins.

Format: Purified

Concentration: Please refer to lot specific datasheet.