PMID- 2835083
OWN - NLM
STAT- MEDLINE
DCOM- 19880614
LR  - 20190613
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 27
IP  - 4
DP  - 1988 Feb 23
TI  - Divalent cations regulate glucagon binding. Evidence for actions on receptor-Ns 
      complexes and on receptors uncoupled from Ns.
PG  - 1111-6
AB  - 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)
FAU - Lipson, K E
AU  - Lipson KE
AD  - Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
FAU - Kolhatkar, A A
AU  - Kolhatkar AA
FAU - Maki, R G
AU  - Maki RG
FAU - Donner, D B
AU  - Donner DB
LA  - eng
GR  - AM 01045/AM/NIADDK NIH HHS/United States
GR  - AM 22121/AM/NIADDK NIH HHS/United States
GR  - AM 30788/AM/NIADDK NIH HHS/United States
GR  - etc.
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Cations, Divalent)
RN  - 0 (Receptors, Gastrointestinal Hormone)
RN  - 0 (Receptors, Glucagon)
RN  - 86-01-1 (Guanosine Triphosphate)
RN  - 9007-92-5 (Glucagon)
RN  - 9G34HU7RV0 (Edetic Acid)
RN  - I38ZP9992A (Magnesium)
SB  - IM
MH  - Animals
MH  - Cations, Divalent
MH  - Cell Membrane/metabolism
MH  - Edetic Acid/*pharmacology
MH  - Glucagon/*metabolism
MH  - Guanosine Triphosphate/pharmacology
MH  - Kinetics
MH  - Liver/*metabolism
MH  - Magnesium/*pharmacology
MH  - Male
MH  - Rats
MH  - Rats, Inbred Strains
MH  - Receptors, Gastrointestinal Hormone/drug effects/*metabolism
MH  - Receptors, Glucagon
EDAT- 1988/02/23 00:00
MHDA- 1988/02/23 00:01
CRDT- 1988/02/23 00:00
PHST- 1988/02/23 00:00 [pubmed]
PHST- 1988/02/23 00:01 [medline]
PHST- 1988/02/23 00:00 [entrez]
AID - 10.1021/bi00404a005 [doi]
PST - ppublish
SO  - Biochemistry. 1988 Feb 23;27(4):1111-6. doi: 10.1021/bi00404a005.