Figure 4: NOMPC is likely a pore-forming subunit of the mechanotransduction channel.

a, Sequence alignment of the putative pore region of NOMPC and its homologues, putative pore helix (black bar) and the putative selective filter (grey bar). Arrows mark the negatively charged Glu 1511 and Asp 1516 residues targeted for mutagenesis. A. suum, Ascaris suum; X. tropicalis, Xenopus tropicalis; D. rerio, Danio rerio. b, The E1511A mutation altered the single-channel conductance of the spontaneous current determined at −60 mV from whole-cell recording in extracellular Na⁺/intracellular Cs⁺ solution (n = 7, 6, 14 from left to right). ***P < 0.001, unpaired t-test. c, The E1511A mutation altered the single-channel I–V curve of spontaneously active channels in the same Na⁺/Cs⁺ solutions. The E1511A mutant channel displayed outward rectification and the E1511K mutation greatly reduced channel activity. d, Sample traces of wild-type and mutant channels in response to 2.8-μm displacement at −100 (dark grey), 0 (black) and 100 (grey) mV. e, The E1511A mutation altered the I–V curve of displacement (2.8 μm)-triggered currents in the same Na⁺/Cs⁺ solutions whereas the E1511K mutation largely eliminated the mechanosensitive current at negative voltage. f, The E1511A mutation altered the I–V curve of pressure-elicited currents in the same Na⁺/Cs⁺ solutions whereas the E1511K mutation largely eliminated the mechanosensitive current (50 mm Hg) at negative voltage. g, The E1511A mutation shifted the reversal potential of spontaneously active NOMPC channels (black bars) and NOMPC channels activated by negative pressure (50 mm Hg, grey bars) in the bi-ionic Na⁺/Cs⁺ conditions (n = 6, 6, 6, 4 from left to right). All error bars denote ± s.e.m.

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