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Title: Two stage binding of glucagon to receptors in rat liver plasma membranes

A homogeneous class of noncooperative receptors in isolated rat hepatocytes undergoes a time- and temperature-dependent conformation change with glucagon binding. A comparable system exists in rat liver plasma membranes. Dissociation assays (30/sup 0/C) quantify the number of receptors in each conformational state. Membranes incubated without GTP demonstrated two dissociation rates. The fraction of hormone bound to the high affinity state increases with incubation time to a limiting value. With isolated membranes and a concentration of 0.2 nM ((/sup 125/I)Iodotyrosyl/sup 10/)glucagon, the fraction of the high affinity form is significantly greater than that found in isolated hepatocytes. Previous work without GTP indicated that a lack of cooperativity characterized the liver membrane system. Incubation of membranes with 0.1 mM GTP increases the K/sub D/ as determined by competition assays while the slope factor (.98 +/- 0.04) indicated noncooperativity. Furthermore, in the presence of GTP a significantly greater proportion of receptors is in the low affinity state while in the absence of GTP more are in the high affinity state. The data are consistent with a mechanism by which GTP diminishes the conversion of the low affinity state to the high affinity state.
Authors:
; ;
Publication Date:
OSTI Identifier:
7189252
Report Number(s):
CONF-8604222-
Journal ID: CODEN: FEPRA
Resource Type:
Conference
Resource Relation:
Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States); Journal Volume: 45:4; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
Research Org:
Indiana Univ., Bloomington
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; GLUCAGON; BIOCHEMICAL REACTION KINETICS; RECEPTORS; AFFINITY; CELL MEMBRANES; IODINE 125; LIVER CELLS; RATS; TEMPERATURE DEPENDENCE; TIME DEPENDENCE; TRACER TECHNIQUES; ANIMAL CELLS; ANIMALS; BETA DECAY RADIOISOTOPES; CELL CONSTITUENTS; DAYS LIVING RADIOISOTOPES; ELECTRON CAPTURE RADIOISOTOPES; HORMONES; INTERMEDIATE MASS NUCLEI; IODINE ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; MAMMALS; MEMBRANE PROTEINS; MEMBRANES; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; PEPTIDE HORMONES; PEPTIDES; POLYPEPTIDES; PROTEINS; RADIOISOTOPES; REACTION KINETICS; RODENTS; SOMATIC CELLS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques