Simplified representation of structural characteristics of voltage-gated K⁺ channel groups.

<p>Voltage-gated K⁺ channel groups are defined according to the clades that arose from the phylogenetic analysis presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137600#pone.0137600.g002" target="_blank">Fig 2</a>. The N-termini of these K⁺ channels are sparsely conserved. Even within channel groups there is a high variability in length (represented by the white to black gradient). Some animal K_out channels show an extended sequence between the first two TMDs. In contrast, all plant Kv-like and animal K_in channels have an extended loop between TMD S2 and S3. Animal K_in channels have the highest number of charged residues in S4, whereas the lowest number is present in plant Kv-like channels. In contrast, plant Kv-like channels feature the highest number of charged residues in the S4-S5 linker, while animal K_out channels hardly possess charged residues in this linker. The most striking structural difference that correlates with channel function is a loop between TMD S5 and the pore region. This loop is only present in plant Kv-like and animal K_in channels. In addition, a small stretch in the loop discriminates between plant K_in and K_out channels.