GluR7 subtype of kainate receptor, type 2 periplasmic-binding fold superfamily; This group contains glutamate receptor domain GluR. These domains are found in the GluR proteins that have been shown to function as L-glutamate activated potassium channels, also known ionotropic glutamate receptors or iGluRs. In addition to two ligand binding core domains, iGluRs typically have a channel-like domain inserted in the middle of the GluR-like domain. Animal iGluRs mediate the ion flux in the synapses of the CNS and can be subdivided into several classes depending on the neurotransmitter specificity and ion conductance properties. Their plant homologs have been shown to function in light signal transduction and calcium homeostasis. The GluR proteins belong to the PBPII superfamily of periplasmic binding proteins that differ in size and ligand specificity, but have similar tertiary structures consisting of two globular subdomains connected by a flexible hinge. They have been shown to bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18033606   1 VSVVLFLVSRFCPYEWHTEEYEDGQIQTNEstNEFGIFNSLWFSLGAFMRQGCDISPRSLSGRIVGGVWWFFTLIIISSY 80
Cdd:cd13723 144 VSCVLFVIARFSPYEWYDAHPCNPGSEVVE--NNFTLLNSFWFGMGSLMQQGSELMPKALSTRIIGGIWWFFTLIIISSY 221

                        90       100
                ....*....|....*....|...
gi 18033606  81 TANLAAFLTVERMVSPIESAEDL 103
Cdd:cd13723 222 TANLAAFLTVERMESPIDSADDL 244

GluR7 subtype of kainate receptor, type 2 periplasmic-binding fold superfamily; This group contains glutamate receptor domain GluR. These domains are found in the GluR proteins that have been shown to function as L-glutamate activated potassium channels, also known ionotropic glutamate receptors or iGluRs. In addition to two ligand binding core domains, iGluRs typically have a channel-like domain inserted in the middle of the GluR-like domain. Animal iGluRs mediate the ion flux in the synapses of the CNS and can be subdivided into several classes depending on the neurotransmitter specificity and ion conductance properties. Their plant homologs have been shown to function in light signal transduction and calcium homeostasis. The GluR proteins belong to the PBPII superfamily of periplasmic binding proteins that differ in size and ligand specificity, but have similar tertiary structures consisting of two globular subdomains connected by a flexible hinge. They have been shown to bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18033606   1 VSVVLFLVSRFCPYEWHTEEYEDGQIQTNEstNEFGIFNSLWFSLGAFMRQGCDISPRSLSGRIVGGVWWFFTLIIISSY 80
Cdd:cd13723 144 VSCVLFVIARFSPYEWYDAHPCNPGSEVVE--NNFTLLNSFWFGMGSLMQQGSELMPKALSTRIIGGIWWFFTLIIISSY 221

                        90       100
                ....*....|....*....|...
gi 18033606  81 TANLAAFLTVERMVSPIESAEDL 103
Cdd:cd13723 222 TANLAAFLTVERMESPIDSADDL 244

The ligand-binding domain of the kainate subtype KA1 of ionotropic glutamate receptors, a member of the type 2 periplasmic-binding fold protein superfamily; This group contains the ligand-binding domain of the KA1 subunit of kainate receptor. While this ligand-binding domain is structurally homologous to the periplasmic binding fold type II superfamily, the N_terminal domain of kainate receptors belongs to the periplasmic-binding fold type I. There are five types of kainate receptors, GluR5, GluR6, GluR7, KA1, and KA2, which are structurally similar to AMPA and NMDA subunits of ionotropic glutamate receptors. KA1 and KA2 subunits can only form functional receptors with one of the GluR5-7 subunits. Moreover, GluR5-7 can also form functional homomeric receptor channels activated by kainate and glutamate when expressed in heterologous systems. Kainate receptors are involved in excitatory neurotransmission by activating postsynaptic receptors and in inhibitory neurotransmission by modulating release of the inhibitory neurotransmitter GABA through a presynaptic mechanism. Kainate receptors are closely related to AMAP receptors. In contrast of AMPA receptors, kainate receptors play only a minor role in signaling at synapses and their function is not well defined.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|....*..
gi 18033606   1 VSVVLFLVSRFCPYEWHTEeYEDGQIQTNESTNEFGIFNSLWFSLGAFMRQGCDISP 57
Cdd:cd13724 144 VSCVLFLVARLTPYEWYSP-HPCAQGRCNLLVNQYSLGNSLWFPVGGFMQQGSTIAP 199