Figure 3
Rules of subunit assembly. Left, the table shows possible trimeric combinations of HyNaCs. HyNaC2 has to be present for a peptide-gated HyNaC. Subunits in the top row and the left row belong to the two subgroups defined by phylogenetic relation. A functional channel activated by Hydra-RFamides is represented by ` + `, a non-functional channel by `-`. Activation by Ca2+ removal but insensitivity to Hydra-RFamides is indicated by `(+)'. Subunit combinations that are co-expressed in Hydra as revealed by ISH are shown on colored background. Orange represents expression at the oral side of the tentacle base, blue at the aboral side and green at the peduncle. Right, scheme illustrating expression sites of HyNaCs. HyNaC, Hydra Na+ channel; ISH, in situ hybridization.