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. (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 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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