7TNM

Complex GNGN2 of AMPA-subtype iGluR GluA2 in complex with auxiliary subunit gamma2 (Stargazin) at low glutamate concentration (20 uM) in the presence of cyclothiazide (100 uM)

Summary for 7TNM

• Entry DOI: 10.2210/pdb7tnm/pdb
• EMDB information: 26011 26012 26013 26014 26015 26016 26017
• Descriptor: Isoform Flip of Glutamate receptor 2,Voltage-dependent calcium channel gamma-3 subunit chimera, GLUTAMIC ACID, CYCLOTHIAZIDE (3 entities in total)
• Functional Keywords: ampa, iglur, stargazin, cryo-em, complex, agonist, positive allosteric modulator, subconductance level, opening, gating, glutamate, membrane protein
• Biological source: Rattus norvegicus (Norway rat); More
• Total number of polymer chains: 4
• Total formula weight: 463633.46

Authors

Yelshanskaya, M.V.,Sobolevsky, A.I. (deposition date: 2022-01-21, release date: 2022-04-20, Last modification date: 2024-11-13)

Primary citation

Yelshanskaya, M.V.,Patel, D.S.,Kottke, C.M.,Kurnikova, M.G.,Sobolevsky, A.I.
Opening of glutamate receptor channel to subconductance levels.
Nature, 605:172-178, 2022

PubMed Abstract: Ionotropic glutamate receptors (iGluRs) are tetrameric ligand-gated ion channels that open their pores in response to binding of the agonist glutamate. An ionic current through a single iGluR channel shows up to four discrete conductance levels (O1-O4). Higher conductance levels have been associated with an increased number of agonist molecules bound to four individual ligand-binding domains (LBDs). Here we determine structures of a synaptic complex of AMPA-subtype iGluR and the auxiliary subunit γ2 in non-desensitizing conditions with various occupancy of the LBDs by glutamate. We show that glutamate binds to LBDs of subunits B and D only after it is already bound to at least the same number of LBDs that belong to subunits A and C. Our structures combined with single-channel recordings, molecular dynamics simulations and machine-learning analysis suggest that channel opening requires agonist binding to at least two LBDs. Conversely, agonist binding to all four LBDs does not guarantee maximal channel conductance and favours subconductance states O1 and O2, with O3 and O4 being rare and not captured structurally. The lack of subunit independence and low efficiency coupling of glutamate binding to channel opening underlie the gating of synaptic complexes to submaximal conductance levels, which provide a potential for upregulation of synaptic activity.

PubMed: 35444281
DOI: 10.1038/s41586-022-04637-w

Experimental method

ELECTRON MICROSCOPY (4.74 Å)