Pulsed electron spin resonance resolves the coordination site of Cu 2+ ions in α1-glycine receptor

Citation for published article

Synthesis, crystal structure, and electronic structure of LiPbSiS: a quaternary thiosilicate with a compressed chalcopyrite-like structure

DOI

10.1016/j.bpj.2010.08.050

Peer Reviewed

1

Document Type

Journal Article

Publication Date

10-20-2010

Publication Title

Biophysical Journal

School

Bayer School of Natural and Environmental Sciences

Primary Author Department

Chemistry and Biochemistry

Abstract

Herein, we identify the coordination environment of Cu2+ in the human α1-glycine receptor (GlyR). GlyRs are members of the pentameric ligand-gated ion channel superfamily (pLGIC) that mediate fast signaling at synapses. Metal ions like Zn2+ and Cu2+ significantly modulate the activity of pLGICs, and metal ion coordination is essential for proper physiological postsynaptic inhibition by GlyR in vivo. Zn2+ can either potentiate or inhibit GlyR activity depending on its concentration, while Cu2+ is inhibitory. To better understand the molecular basis of the inhibitory effect we have used electron spin resonance to directly examine Cu2+ coordination and stoichiometry. We show that Cu2+ has one binding site per α1 subunit, and that five Cu2+ can be coordinated per GlyR. Cu2+ binds to E192 and H215 in each subunit of GlyR with a 40 μM apparent dissociation constant, consistent with earlier functional measurements. However, the coordination site does not include several residues of the agonist/antagonist binding site that were previously suggested to have roles in Cu2+ coordination by functional measurements. Intriguingly, the E192/H215 site has been proposed as the potentiating Zn 2+ site. The opposing modulatory actions of these cations at a shared binding site highlight the sensitive allosteric nature of GlyR. © 2010 by the Biophysical Society.

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