Evidence for the involvement of a carboxyl group in the vicinity of the MK801 and magnesium ion binding site of the N-methyl-D-aspartate receptor

Biochem Pharmacol. 1993 Feb 9;45(3):605-10. doi: 10.1016/0006-2952(93)90133-h.


A series of protein modifying reagents were tested for their effects on the specific binding of [3H]MK801 to adult rat brain membranes. N-Bromosuccinimide, acetyl imidazole, 2,3-butanedione, 5,5'-dithiobis-(2-nitrobenzoic acid) and dithiothreitol all had no significant effect on binding. The carboxylic acid residue modification reagent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC), inhibited [3H]MK801 specific binding in a dose-dependent manner with an IC50 = 1.9 mM. The inhibition by EDAC was due to a decrease in the Bmax with no change in KD. The inhibition of [3H]MK801 binding by EDAC was not prevented by prior incubation with competitive antagonists. Protection against EDAC inactivation was obtained, however, in a dose-dependent manner by preincubation with the divalent cations, Ca2+ and Mg2+, but not Zn2+. These results suggest that EDAC modifies an important carboxyl group located within the voltage-dependent Mg2+ binding site of the N-methyl-D-aspartate receptor. This modification yields a decrease in the specific [3H]MK801 binding activity thus demonstrating a close association between the two allosteric regulatory sites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / chemistry
  • Animals
  • Binding Sites
  • Binding, Competitive
  • Brain Chemistry
  • Carbodiimides / pharmacology
  • Dizocilpine Maleate / antagonists & inhibitors
  • Dizocilpine Maleate / chemistry*
  • Dose-Response Relationship, Drug
  • Drug Design
  • Magnesium / chemistry*
  • Rats
  • Rats, Wistar
  • Receptors, N-Methyl-D-Aspartate / chemistry*


  • Amino Acids
  • Carbodiimides
  • Receptors, N-Methyl-D-Aspartate
  • 1-ethyl-3-(3-dimethylaminoethyl)carbodiimide
  • Dizocilpine Maleate
  • Magnesium