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.
Knuhtsen
S
S
Institut National de la Santé et de la Recherche Médicale U151, CHU Rangueil, Toulouse, France.
Esteve
J P
JP
Cambillau
C
C
Colas
B
B
Susini
C
C
Vaysse
N
N
D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D007525:Isoelectric Focusing; D008297:Male; D010179:Pancreas / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017481:Receptors, Somatostatin; D012995:Solubility; D013004:Somatostatin / Q000378:metabolism; D013873:Thionucleotides / Q000378:metabolism
D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013004:Somatostatin; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins