Fig. 6: Arg553 occupies the putative cNMP pocket for MtCNGC15b.

a Structural alignment between the CNBD of MtCNGC15b and the cGMP-bound human CNGA1. The corresponding region of the cGMP binding site in MtCNGC15b is negatively charged in comparison with human CNGA1. b The basic side chain of Arg553 is compatible with the negatively charged pocket of MtCNGC15b composed by Glu533 and Glu534. The Arg553 is conserved in Medicago but not representative animal CNG channels. c Mutagenesis of Arg553 to different amino acids decreases the Ca²⁺ currents. 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. d Sequence and structure clustering results of 726 sequences that share over 80% similarity with CNG channels from C. elegans, H. sapiens, and M. truncatula. The representative predicted structures are aligned to MtCNGC15b with the entries number listed.