Divalent cations regulate glucagon binding. Evidence for actions on receptor-Ns complexes and on receptors uncoupled from Ns

Lipson, K. E., Kolhatkar, A. A., Maki, R. G., Donner, D. B. (February 1988) Divalent cations regulate glucagon binding. Evidence for actions on receptor-Ns complexes and on receptors uncoupled from Ns. Biochemistry, 27 (4). pp. 1111-6. ISSN 0006-2960 (Print)0006-2960 (Linking)

URL: https://www.ncbi.nlm.nih.gov/pubmed/2835083
DOI: 10.1021/bi00404a005

Abstract

The effects of Mg2+ or ethylenediaminetetraacetic acid (EDTA) on 125I-glucagon binding to rat liver plasma membranes have been characterized. In the absence of guanosine 5'-triphosphate (GTP), maximal binding of 125I-glucagon occurs in the absence of added Mg2+. Addition of EDTA or Mg2+ diminishes binding in a dose-dependent manner. In the presence of GTP, maximal binding occurs in the presence of 2.5 mM Mg2+ (EC50 = 0.3 mM) while EDTA or higher concentrations of Mg2+ diminish binding. Response to exogenous Mg2+ or EDTA depends on the concentration of Mg2+ in the membranes and may vary with the method used for membrane isolation. Solubilized 125I-glucagon-receptor complexes fractionate on gel filtration columns as high molecular weight, GTP-sensitive complexes in which receptors are coupled to regulatory proteins and lower molecular weight, GTP-insensitive complexes in which receptors are not coupled to other components of the adenylyl cyclase system. In the absence of GTP, 40 mM Mg2+ or 5 mM EDTA diminishes receptor affinity for hormone (from KD = 1.2 +/- 0.1 nM to KD = 2.6 +/- 0.3 nM) and the fraction of 125I-glucagon in high molecular weight receptor-Ns complexes without affecting site number (Bmax = 1.8 +/- 0.1 pmol/mg of protein). Thus, while GTP promotes disaggregation of receptor-Ns complexes, Mg2+ or EDTA diminishes the affinity with which these species bind hormone. In the presence of GTP, hormone binds to lower affinity (KD = 9.0 +/- 3.0 nM), low molecular weight receptors uncoupled from Ns.(ABSTRACT TRUNCATED AT 250 WORDS)

Item Type: Paper
Uncontrolled Keywords: Animals Cations, Divalent Cell Membrane/metabolism Edetic Acid/*pharmacology Glucagon/*metabolism Guanosine Triphosphate/pharmacology Kinetics Liver/*metabolism Magnesium/*pharmacology Male Rats Rats, Inbred Strains Receptors, Gastrointestinal Hormone/drug effects/*metabolism Receptors, Glucagon
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > glucosinolates
structural biology
CSHL Authors:
Communities: CSHL labs > Maki lab
Depositing User: Matt Covey
Date: 23 February 1988
Date Deposited: 26 Oct 2016 21:24
Last Modified: 26 Oct 2016 21:24
Related URLs:
URI: http://repository.cshl.edu/id/eprint/33637

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