Product Number: P-4201
Product Name: E. coli heat-stable enterotoxin STa (5-18)
Storage Temp: Below 0°C
Specifications: Lyophilized peptide in 10µG vials
Purity ≥ 95%
Confirmed by HPLC
Fully active in cGMP accumulation assay
Fully soluble in PBS or other aqueous buffer ≥ 1 mg/ml
Unit Definition: One unit is the amount of toxin which induces the accumulation of 550 pmoles of cGMP/mg protein in intact T84 cells over 10 minutes (Basal <1.0).
Biochemical/
Physiological Actions:
STa has a structure maintained by a specific pairing of 3 disulfide bridges. STa has a specific pairing of 3 disulfides which constrains the peptide in its bioactive conformation and confers its characteristic heat stability.(1-3) STa has been demonstrated to bind to guanylyl cyclase-C receptors located on enterocytes and metastatic colorectal cancer cells.(2,4,5,6) STa causes diarrhea in humans by binding to GC-C and triggering the production of cyclic GMP. Endogenous ligands for the STa receptor include guanylin , extracted from intestine, and uroguanylin from urine. These peptides may have a role in the regulation of fluids and electrolytes. Protein Kinase C (PKC) phosphorylates and activates the STa receptor/guanylyl cyclase in vitro and in vivo. As a result, stimulators of PKC synergistically enhance STa effects on cGMP and secretion.
Literature References:  
1.   Giannella, R.A., Escherichia coli heat-stable enterotoxins, guanylins, and their receptors: what are they and what do they do, J. Lab. Clin. Med. 125, 173-181 (1995)
  2. Lucas, K.A. et al, Guanylyl Cyclases and Signaling by Cyclic GMP, Pharm. Reviews Vol.52, No.3, 375-413 (2000)
  3. Wolfe, H. R., et al, A Comparative Molecular Field Analysis (COMFA) of the Structural Determinants of Heat-Stable Enterotoxins Mediating Activation of Guanylyl Cyclase C, J.Med. Chem., 2002, 45,1731-1734
  4. Carrithers, S.L., et al, Escherichia Coli Heat-Stable Enterotoxin Receptors, A Novel marker for Colorectal Tumors, Dis. Colon Rectum, Vol.39, No.2, 171-181 (1996)
  5. Pitari, G.M., et al, Gualylyl cyclase C agonists regulate progression through the cell cycle of human colon carcinoma cells, PNAS, July 3, 2001, Vol. 98, no. 14, 7846-7851
  6. Wolfe, H.R., et al, In Vivo Imaging of Human Colorectal Cancer Xenografts in Immunodeficient Mice Using a Guanylyl Cyclase C-Specific Ligand, J. N. Med., Vol. 43, No. 3, 392-399, (2002)