title: An active-site histidine of NR1/2C mediates voltage-independent inhibition by zinc.
abstract: Endogenous zinc is an important modulator of ion channels of the central nervous system. To understand mechanisms of zinc inhibition, cloned heteromeric N-methyl-D-aspartate receptors (primary subunit NR1 with secondary subunits NR2A, NR2C or NR2D) were expressed in Xenopus oocytes and studied under two-electrode voltage-clamp. Voltage-independent inhibition of NR1/2A heteromers by nanomolar concentrations of extracellular zinc was observed in barium-containing perfusion solutions. In contrast, voltage-independent zinc inhibition of NR1/2C heteromers occurred with lower affinity. Zinc inhibition data from NR1/2D heteromers was fit well with a voltage-independent one-site model and resembled that previously reported for NR1/2B. Reduction of zinc inhibition of NR1/2C heteromers was seen after labeling with the histidine-modifying reagent diethylpyrocarbonate. This finding suggests that the NR1/2C heteromeric ion channel contains an active-site histidine responsible for zinc inhibition.
authors.affiliation: Department of Anesthesia, University of California, School of Medicine, San Francisco 94143-0542, USA. andy_gray.ucsfa@quickmail.ucsf.edu
authors.forename: A T
authors.initials: AT
authors.lastname: Gray
authors.forename: D J
authors.initials: DJ
authors.lastname: Leonoudakis
authors.forename: C S
authors.initials: CS
authors.lastname: Yost
mesh_terms: D000818:Animals; D001665:Binding Sites; D006639:Histidine / Q000737:chemistry*; D009865:Oocytes / Q000737:chemistry; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000502:physiology*; D014982:Xenopus laevis; D015032:Zinc / Q000502:physiology*
chemical_list: D010446:Peptide Fragments; D016194:Receptors, N-Methyl-D-Aspartate; D006639:Histidine; D015032:Zinc