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. Author manuscript; available in PMC: 2016 Mar 14.
Published in final edited form as: Annu Rev Physiol. 2009;71:59–82. doi: 10.1146/annurev.physiol.010908.163204

Figure 2.

Figure 2

Phylogenetic tree of P-loop-containing proteins from Arabidopsis thaliana (dark blue), rice (Oryza sativa; red ), and Chlamydomonas reinhardtii (light blue). Where applicable, schematized membrane topologies are indicated: P-loop, green; transmembrane domain 4 (TM4) including positively charged amino acids, orange; K+ selectivity filter residues, magenta. Cytosolic elements such as long C-terminal domains, cyclic nucleotide (cNMP) binding domains, or ankyrin repeats are not depicted. The photosynthetic alga C. reinhardtii has a unique set of ion channel genes (see Reference 105 and text). The P-loop-containing channels from C. reinhardtii all have a positively charged TM4, but only five (179857, 144365, 189793, 144354, and 165774) have a K+ selectivity filter. Because these do not form a clade, and because the C. reinhardtii channels are poorly resolved in general, they could not be attributed to specific classes. Scale indicates the number of amino acid substitutions per site. Kv IR, inward-rectifying K+ channel; Kv OR, outward-rectifying K+ channel; CNGC, cyclic nucleotide–gated channel; TPK, two-pore K+ channel.