Antigen: Recombinant human full length p23 protein · Clone designation: JJ6 · Host: Mouse · Isotype: IgG₁ · Application(s): WB,IP, and ELISA · M_r: 23 kDa · p23 is a highly conserved ubiquitous protein, known to have an important function as a co-chaperone for the Hsp90 chaperoning system.¹ Studies have revealed that p23 is a small protein (18-25 kDa) with a simple structure.^2,3 p23 does not have any structural homology with any other known proteins.¹ p23 was first discovered as a part of the Hsp90-progesterone receptor complex along with Hsp70, p54, and p50.¹ p23 is a phospho-protein, which is highly acidic and has an aspartic acid-rich C-terminal domain.¹ Numerous studies have found p23 to be associated with other client proteins like Fes tyrosine kinase⁴, the heme-regulated kinase HRI⁵, Hsf1 transcription factor⁴, aryl hydrocarbon receptor⁴, telomerase⁶, and Hepadnavirus reverse transcriptase.⁷ In spite of several years of study, the exact functional significance of p23 is still not clear.p23 is identical to cytosolic prostaglandin E synthase (cPGES), coverting to PGH₂ to PGE₂ downstream of COX-1.⁸ p23 is also thought to be involved in the adenosine triphosphate-mediated Hsp90 binding of client proteins.⁹ Since many Hsp90 client proteins are involved in oncogenic survival signaling, a recent study has concluded p23 to be a promising target in leukemic apoptosis.¹⁰ Hsp90 and its co-chaperone p23 are certainly among the emerging anti-tumor targets in oncology.

1 Johnson, J.J., Beito, T.G., Krco, C.J., et al. Characterization of a novel 23-kilodalton protein of unactive progesterone receptor complexes. Mol Cell Biol 14(3) 1956-1963 (1994).

2 Weikl, T., Abelmann, K., and Buchner, J. An unstructured C-terminal region of the Hsp90 co-chaperone p23 in important for its chaperone function. J Mol Biol 293 685-691 (1999).

3 Weaver, A.J., Sullivan, W.P., Felts, S.J., et al. Crystal structure and activity of human p23, a heat shock protein 90 co-chaperone. J Biol Chem 275(30) 23045-23052 (2000).

4 Nair, S.C., Toran, E.J., Rimerman, R.A., et al. A pathway of multi-chaperone interactions common to diverse regulatory proteins: estrogen receptor, Fes tyrosine kinase, heat shock transcription factor Hsf1, and the aryl hydrocarbon receptor. Cell Stress Chaperones 1(4) 237-250 (1996).

5 Xu, Z., Pal, J.K., Thulasiraman, V., et al. The role of the 90-kDa heat-shock protein and its associated cohorts in stabilizing the heme-regulated eIF-2α kinase in reticulocyte lysates during heat stress. Eur J Biochem 246 461-470 (1997).

6 Holt, S.E., Aisner, D.L., Baur, J., et al. Functional requirement of p23 and Hsp90 in telomerase complexes. Genes Dev 13 817-826 (1999).

7 Hu, J., Toft, D., Anselmo, D., et al. In vitro reconstitution of functional hepadnavirus reverse transcriptase with cellular chaperone proteins. J Virol 76(1) 269-279 (2002).

8 Tanioka, T., Nakatani, Y., Semmyo, N., et al. Molecular identification of cytosolic prostaglandin E₂ synthase that is functionally coupled with cyclooxygenase-1 immediate prostaglandin E₂ biosynthesis. J Biol Chem 275 32775-32782 (2000).

9 Felts, S.J., and Toft, D.O. p23, a simple protein with complex activities. Cell Stress Chaperones 8(2) 108-113 (2003).

10 Gausdal, G., Gjertsen, B.T., Fladmark, K.E., et al. Caspase-dependent, geldanamycin-enhanced cleavage of co-chaperone p23 in leukemic apoptosis. Leukemia 18 1989-1996 (2004).

Johnson, J.J., Beito, T.G., Krco, C.J., et al. Characterization of a novel 23-kilodalton protein of unactive progesterone receptor complexes. Mol Cell Biol 14(3) 1956-1963 (1994).

Gausdal, G., Gjertsen, B.T., Fladmark, K.E., et al. Caspase-dependent, geldanamycin-enhanced cleavage of co-chaperone p23 in leukemic apoptosis. Leukemia 18 1989-1996 (2004).

Felts, S.J., and Toft, D.O. p23, a simple protein with complex activities. Cell Stress Chaperones 8(2) 108-113 (2003).

Hu, J., Toft, D., Anselmo, D., et al. In vitro reconstitution of functional hepadnavirus reverse transcriptase with cellular chaperone proteins. J Virol 76(1) 269-279 (2002).

Holt, S.E., Aisner, D.L., Baur, J., et al. Functional requirement of p23 and Hsp90 in telomerase complexes. Genes Dev 13 817-826 (1999).

Xu, Z., Pal, J.K., Thulasiraman, V., et al. The role of the 90-kDa heat-shock protein and its associated cohorts in stabilizing the heme-regulated eIF-2α kinase in reticulocyte lysates during heat stress. Eur J Biochem 246 461-470 (1997).

Nair, S.C., Toran, E.J., Rimerman, R.A., et al. A pathway of multi-chaperone interactions common to diverse regulatory proteins: estrogen receptor, Fes tyrosine kinase, heat shock transcription factor Hsf1, and the aryl hydrocarbon receptor. Cell Stress Chaperones 1(4) 237-250 (1996).

Weaver, A.J., Sullivan, W.P., Felts, S.J., et al. Crystal structure and activity of human p23, a heat shock protein 90 co-chaperone. J Biol Chem 275(30) 23045-23052 (2000).

Weikl, T., Abelmann, K., and Buchner, J. An unstructured C-terminal region of the Hsp90 co-chaperone p23 in important for its chaperone function. J Mol Biol 293 685-691 (1999).

Tanioka, T., Nakatani, Y., Semmyo, N., et al. Molecular identification of cytosolic prostaglandin E₂ synthase that is functionally coupled with cyclooxygenase-1 immediate prostaglandin E₂ biosynthesis. J Biol Chem 275 32775-32782 (2000).

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