Comparison of Xenopus IRBP with itself and known IRBPs. A) Dotplot of Xenopus IRBP, comparing the protein sequence against itself. The boxes on the ordinate and abscissa are schematic diagrams of modules 1 through 4. The numbering on the axes correspond with the amino acid residues in Figure 2. The diagonal lines indicate regions of internal similarity, and hence the presence of the four modules. B) Distance tree showing the relationship between Xenopus, human, bovine, goldfish and zebrafish IRBPs. The branch lengths are drawn to scale and the values at the nodes indicate the number of times a grouping occurred in a set of 100 bootstrap values. The long distance separating the teleosts from amphibians is due in part to the teleosts having only two modules.