Solubilization and characterization of active somatostatin receptors from rat pancreas.
Somatostatin receptors were solubilized from rat pancreatic membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS). The binding of an iodinated somatostatin analog [125I-Tyr3]SMS to the soluble fraction was time-dependent, saturable, and reversible. Scatchard analysis of equilibrium binding data indicated that the soluble extract contained a single class of somatostatin binding sites with a Kd of 0.3 nM and a Bmax of 210 fmol/mg. As observed with membrane-bound receptors, soluble binding receptors were sensitive to the GTP analog GTP gamma S indicating that they are functionally linked to a G protein. A molecular weight of about 400,000 was determined for soluble receptors under native conditions by gel filtration. In denaturing gel electrophoresis, photoaffinity labeling of soluble receptors identified a major protein of Mr = 100,000 and two minor proteins of Mr = 56,000 and 21,000. Isoelectric focusing of soluble receptors revealed that the somatostatin receptor is an acidic protein with pI 4. 8. The soluble somatostatin receptor is a glycoprotein which can be specifically bound to the wheat germ agglutinin lectin and eluted by triacetyl-chitotriose.[1]References
- Solubilization and characterization of active somatostatin receptors from rat pancreas. Knuhtsen, S., Esteve, J.P., Cambillau, C., Colas, B., Susini, C., Vaysse, N. J. Biol. Chem. (1990) [Pubmed]
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