Fig. 1

Design of Kcv_ATCV-1/GluA1chimeras. a The cartoon depicting the topology of a subunit of the Kcv_ATCV-1 (blue), GluA1 (brown), and the chimera GluATCV harboring the membrane-spanning domain of the Kcv_ATCV-1. Amino-terminal domain (NTD), ligand-binding domain (LBD), C- terminal domain (CTD), pore helix (P), transmembrane domains (TM respectively M in case of GluA1), substrate-binding-protein (SBP, dark brown). Permeant cations are indicated. b Structural overlay TM of Kcv_ATCV-1 and GluA2. TM1 and pore helix as well as M1 and M2 of GluA2 are transparent. TM of Kcv_ATCV-1 (TM2) and GluA2 (M3) are in full color. Helices were superimposed by aligning main-chain atoms of TM2 segments from Kcv_ATCV-1 model (see Methods) on crystal structure of M3 domain of GluA2 subunit (Protein Database entry 3KG2²⁰) (side view). Backbones and residues of subunits are illustrated in ribbon representations (blue: Kcv_ATCV-1; brown: GluA2) within iGluRs conserved SYTANLAAF region (green) and position of G77 and F78 of Kcv_ATCV-1 (red). c Design of GluATCV constructs. Partial sequence alignment of GluA1, GluA2, and different GluATCV constructs. Illustration of amino acid cutting sites of different GluA1/Kcv_ATCV-1 chimeras (GluATCV). Chimeras harboring different lengths of the SYTANLAAF motif  (green) with corresponding residue numbering of mature subunits (Kcv_ATCV-1 blue; GluA1 brown) are indicated. GluATCVlong (linker length + 13 aa); GluATCVshort (linker length + 8 aa), and GluATCV (no linker). Residues found at cutting sites and within the SYTANLAAF motif are highlighted. Secondary structure elements found are illustrated above the sequence. d Functional characterization of chimeric GluATCV constructs. Representative whole-cell currents of glutamate (Glu) responses and Ba²⁺ inhibition of GluA1/Kcv_ATCV-1 chimeras upon heterologous expression in Xenopus oocytes recorded at −70 mV membrane potential. Oocytes expressing GluATCVshort and GluATCV were superfused with the indicated concentration of glutamate in the absence and presence of 500 µM Ba²⁺. Current traces illustrating inhibitory effects of Ba²⁺ in both chimera. Note that K⁺-specific blocker Ba²⁺ inhibits both glutamate-induced currents elicited from GluATCV and leak current in GluATCVshort expressing oocytes. Black dotted line indicates Ba²⁺ insensitive leakage current. Bars show timepoint and duration of the application. Gray dotted line and arrows indicate glutamate induced current (I_Glu) and barium blockable current (I_Ba)