Background: Low molecular weight protein tyrosine phosphtases, including the human red cell phosphatase, HCPTP, are widely expressed cytosolic proteins of approximately 18kDa that exist in distinct isoforms and are highly selective for phosphotyrosine over phosphoserine or phosphotyrosine. The HCPTP-A and HCPTP-B proteins expressed in human red cells and placenta are fast and slow forms of red cell acid phosphatase5. Like other tyrosine phosphatases, HCPTP is sensitive to inhibition by vanadate, and has a catalytic mechanism that involves formation of a cystinyl-phosphate intermediate6. The crystal structure of the bovine heart derived enzyme BHPTP shows a four-stranded central parallel b sheet with flanking a helices and an active site cysteine residue in the typical tyrosine phosphatase sequence context, CXXXXXR.
Biological actions and cellular substrates have not been fully elucidated. It is expressed in a wide range of cell types, and structural homologues are expressed in yeast. A catalytically inactive LMW-PTP functions to promote cell division and binds to tyrosine-phosphorylated PDGF receptors1. The HCPTPA isoform interacts with receptor tyrosine kinases, EphB1 and VEGFR2 (flk-1)2,4. Its overexpression inhibits VEGF-induced endothelial proliferation and migration, and its recruitment to EphB1 complexes is crucial to downstream signaling between EphB1 and integrins that mediate cell-matrix attachment3.
Immunogen: The human protein, HCPTPA (GB Accession #M83653) was subcloned into pRSET to express a His6 N terminal fusion protein. This protein was expressed in E. coli and purified to homogeneity on Ni affinity matrix.
Purification Method: Ammonium Sulfate Precipitation.
Formulation: Provided as solution in phosphate buffered saline with 0.08% sodium azide.
References: 1. Chiarugi, P., Cirri, P., Raugei, G., Camici, G., Dolfi, F., Berti, A., and Ramponi, G. (1995). PDGF receptor as a specific in vivo target for low M(r) protein tyrosine phosphatase. FEBS Letters 372, 49-53.
2. Huang, L., Sankar, S., Lin, C., Kontos, C.D., Schroff, A.D., Cha, E.H., Feng, S.M., Li, S.F., Yu, Z., Van Etten, R.L., Blanar, M.A., and Peters, K.G. (1999). HCPTPA, a Protein Tyrosine Phosphatase That Regulates Vascular Endothelial Growth Factor Receptor-mediated Signal Transduction and Biological Activity. J.Biol.Chem. 274, 38183-38188.
3. Huynh-Do, U., Stein, E., Lane, A.A., Liu, H., Cerretti, D.P., and Daniel, T.O. (1999). Surface densities of ephrin-B1 determine EphB1-coupled activation of cell attachment through alphavbeta3 and alpha5beta1 integrins. EMBO J. 18, 2165-2173.
4. Stein, E., Lane, A.A., Cerretti, D.P., Schoecklmann, H.O., Schroff, A.D., Van Etten, R.L., and Daniel, T.O. (1998). Eph receptors discriminate specific ligand oligomers to determine alternative signaling complexes, attachment, and assembly responses. Genes Dev. 12, 667-678.
5. Wo, Y.-Y., McCormack, A.L., Shabanowitz, J., Hunt, D.F., Davis, J.P., Mitchell, G.L., and Van Etten, R.L. (1992). Sequencing, cloning, and expression of human red cell-type acid phosphatase, a cytoplasmic phosphotyrosyl protein phosphatase. J Biol Chem 267, 10856-10865.
6. Zhang, M., Stauffacher, C.V., and VanEtten, R.L. (1995). The three dimensional structure, chemical mechanism and function of the low molecular weight protein tyrosine phosphatases. Adv.Prot.Phosphatases 9, 1-23.
UniProt: P24666 (Human)
Q9D358 (Mouse)
P41498 (Rat)
P11064 (Bovine).
Caution: This product is intended FOR RESEARCH USE ONLY, and FOR TESTS IN VITRO, not for use in diagnostic or therapeutic procedures involving humans or animals.
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