Fig. 3. Phylogenetic analysis of the cation proton antiporter (CPA) superfamily. The phylogenetic tree was constructed using maximum likelihood (ML) analysis and is shown as a ML-distance tree. It was deduced from an alignment of 65 sequences of prokaryotic and eukaryotic CPA genes and is arbitrarily rooted with the E. coli NhaA sequence. ML support values are shown at branch nodes. Background highlighting: CPA1 genes, purple; CPA2 genes, yellow; further CPA2 gene highlighting: bacteria, red; vertebrate, green; nematode, orange; insect, blue. The scale bar indicates the estimated number of amino acid substitutions per site. Abbreviations as in Table 1.