Fig. 3: The coordination between VSD and PD of MtCNGC15b.

a Structural differences between MtCNGC15b with human CNGA1 or C. elegans TAX-4. b Three pairs of disulfide bonds are located at the nuclear envelop lumen side. The Cys99-Cys281 mediated the interaction between VSD and PD. c Sequence and structural comparison of the extracellular cysteine pairs in representative plant CNGCs and animal CNG channels. The Cys99-Cys281 mediated-disulfide bond is specifically observed in plant CNGCs. d Disruption of the identified three disulfide bonds decreases the Ca²⁺ currents. Particularly, mutations of the Cys99-Cys281 pair nearly abolish the channel activity. Current–voltage relationship of MtCNGC15b and its variants currents recorded from Xenopus oocytes. Command voltages were applied in 10-mV steps between 0 mV and –160 mV. Data are presented as means ± SEM.