Fig. 1.

Phylogenetic tree of 325 OPT superfamily proteins based on the ClustalX multiple alignment shown in Fig. S1 and drawn using the FigTree program. Clusters 1–5 are labeled with their respective subclusters. Subclusters 1A–3B are putative peptide transporters, while some members of subclusters 4A–5D are known to be iron-siderophore transporters. Protein abbreviations are presented in Table 1 in the same order as shown in the tree, together with the characteristics of these proteins. The positions of the individual proteins are revealed in the dendrogram shown in Fig. S2