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. 2020 May 15;3:240. doi: 10.1038/s42003-020-0951-z

Fig. 3. Role of pore constriction in anion selectivity.

Fig. 3

a Cross-sections of the surface representation for the N-terminal half of the HsLRRC8D subunits, showing the ion channel pore. The four subunits are colored according to Fig. 1b, and are shown in cartoon representations. b Close-up views of the pore constrictions formed by the extracellular and TM regions of the HsLRRC8D (left) and HsLRRC8A (PDB ID: 5ZSU)15 (right) structures. For clarity, only two diagonal subunits viewed parallel to the membrane are shown. The side chains of the pore-lining amino acid residues from NTH, TM1, and EL1H are depicted in stick representations. The distances between the residues involved in the pore constrictions are shown. c The pore radii for the HsLRRC8D and HsLRRC8A (PDB ID: 5ZSU)15 structures. The pore size was calculated with the program HOLE37. d Sequence alignment of the human LRRC8 isoforms around the pore constriction formed by the extracellular and TM regions. The amino acid sequences were aligned using Clustal Omega38, and are shown using ESPript339. The NTH, TM1, and EL1H regions of HsLRRC8D are labeled above the alignments. For the sequence alignment, the following human LRRC8 isoforms were used: HsLRRC8A, NCBI Reference sequence number: NP_062540.2; HsLRRC8B, NP_056165.1; HsLRRC8C, NP_115646.2; HsLRRC8D, NP_060573.2; and HsLRRC8E, AAH70089.1. The amino acid residue involved in the pore constriction on the extracellular side is highlighted with an orange dot. e Representative current traces of swelling-induced currents in response to voltage ramps of −100 to +100 mV, in one LRRC8−/− cell co-transfected with HsLRRC8A wild type and HsLRRC8D wild type (left), and another LRRC8−/− cell co-transfected with HsLRRC8A wild type and HsLRRC8D F143R mutant (right). f Relative anion selectivity (Px/PCl) calculated from the shifts of the reversal potential induced by the replacement of chloride ions with other anions. Data are means ± SEM (n = 5–6). *P < 0.05 compared to the data from LRRC8−/− cells co-transfected with HsLRRC8A wild type and HsLRRC8D wild type. P values were calculated by the Student’s t test.