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.
- Research Organization:
- Indiana Univ., Bloomington
- OSTI ID:
- 7189252
- Report Number(s):
- CONF-8604222-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:4; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
- Country of Publication:
- United States
- Language:
- English
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RECEPTORS
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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
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KINETICS
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MEMBRANE PROTEINS
MEMBRANES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PEPTIDES
POLYPEPTIDES
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RADIOISOTOPES
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RODENTS
SOMATIC CELLS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques