Fig. 2. Relationships of sea urchin T-domain proteins. (A) A phylogenetic tree of T domains. A molecular phylogenetic tree was constructed using the NJ method by a computer program (Genetyx, Software Development). The branch length is proportional to the number of amino acid substitutions. The number at each branch indicates the values of expected substitution of amino acid residues. (B) Alignment of the amino acid sequences of the T domain of T-brain subfamily members. Asterisks (^*) indicate that all of the six T-brain proteins have an identical amino acid.