Probing the Mg2+ blockade site of an N-methyl-D-aspartate (NMDA) receptor with unnatural amino acid mutagenesis.
The N -methyl-D-aspartate (NMDA) receptor plays a central role in learning and memory in the mammalian CNS. At normal neuronal resting membrane potentials, the pore of this glutamate-gated ion channel is blocked by a Mg(2+) ion. Previous work suggests that the Mg(2+) binding site is quite novel, involving several asparagine residues and a cation-pi interaction between Mg(2+) and a conserved tryptophan in the pore. Using unnatural amino acid mutagenesis, we show that no such cation-pi interaction exists. The implicated tryptophan instead appears to play a structural role that can only be fulfilled by a rigid, flat, hydrophobic residue. This is the first demonstration of unnatural amino acid incorporation in the NMDA receptor, and it opens the way for future investigations of this pivotal neuroreceptor.
McMenimen
Kathryn A
KA
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Dougherty
Dennis A
DA
Lester
Henry A
HA
Petersson
E James
EJ
D019943:Amino Acid Substitution / Q000235:genetics; D000596:Amino Acids / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D005260:Female; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed / Q000379:methods*; D009865:Oocytes; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
D000596:Amino Acids; D016194:Receptors, N-Methyl-D-Aspartate; D014364:Tryptophan; D008274:Magnesium