Phylogenetic trees of K+-channel types. (a) Voltage-dependent K+ channels; (b) inward rectifier K+ channels. Sequences were aligned using ClustalX. Six transmembrane channel sequences are confined to the region spanning the first through the sixth transmembrane domain, so as to remove highly variable sequence. Similarly, variable amino-terminal sequences of inward rectifier K+ channels were removed in order to exclude highly variable sequence. The culled alignments were then used to construct a maximum likelihood tree in (a) and a neighbor-joining tree in (b). The tree in (a) uses the Escherichia coli KCH K+ channel homolog (Genbank accession number 808903) as an outgroup. For the tree in (b), the bootstrap values above the branch before each node are based on 1,000 replicates and are a measure of robustness at each node. The Jones-Taylor-Thornton amino-acid substitution matrix was used in the maximum likelihood calculations from PHYLIP. The sequences in (b) are shown without the punctuation such that MouseKIR22 = Mouse KIR2.2, and so on. The sequence named CEL is Caenorhabditis elegans inward rectifier K+ channel (gi 7511460).