Purification of a pituitary receptor for somatostatin. The utility of biotinylated somatostatin analogs.

摘要: A somatostatin (SRIF) receptor and its associated Gi regulatory proteins was purified from GH4C1 rat pituitary cells by: 1) saturation of the membrane-bound with biotinyl-NH-[Leu8,D-Trp22,Tyr25] SRIF28 (bio-S28); 2) solubilization receptor-ligand (R.L) complex deoxycholate-lysophosphatidylcholine (D.L); 3) adsorption solubilized to immobilized streptavidin; 4) elution G-protein by GTP. The receptor, a glycoprotein an average M(r) 85,000, then substantial homogeneity on wheat germ agglutinin. 85-kDa identified as SRIF several criteria. (a) It had same size chemically cross-linked R.[125I]L complex. (b) Yield protein increased plateaued in range bio-S28 concentrations where specific high affinity binding reached saturation. (c) copurified appropriate subunits. two other values 35,000 40,000, sizes G beta alpha, did not appear eluates control streptavidin columns done receptors loaded nonbiotinylated S14. 40-kDa alpha ADP-ribosylation [32P]NAD catalyzed pertussis toxin. (d) Both [35S]methionine-labeled were reduced about 38 kDa endoglycosidase F. (e) Amino acid sequence nearly identical that recently cloned subtype.