Distribution of BTB proteins in eukarytoic genomes. (a) Representation of BTB proteins in selected sequenced genomes. Twelve of the seventeen genomes we searched are represented, showing each type of BTB protein architecture as bar segments. Data for Apis mellifera, Canis familiaris, Gallus gallus, Pan troglodytes and Xenopus tropicalis are available at . Several lineage-specific expansions are evident: BTB-ZF and BBK proteins in the vertebrates; the MATH-BTB proteins in the worm; the BTB-NPH3 proteins in the plant; the Skp1 proteins in the plant and worm; and the T1 proteins in worm and vertebrates. In the Dictyostellium discoideum genome, a single star indicates five BTB-kelch proteins that do not contain the BACK domain, and a double star indicates two MATH-BTB proteins that also contain ankyrin repeats. (b) Phylogenetic relationship of analyzed genomes. Adapted from . The total number of BTB proteins is shown above each genome.