Figure 2.

Domain structure and phylogenetic tree of human dickkopf proteins. A: Each dickkopf (DKK) contains two cysteine-rich domains, each of which is separated by a linker region of various lengths. The amino-terminal cysteine-rich domain (Cys-1) domains are unique to each DKK, whereas the carboxyl-terminal cysteine-rich domain (Cys-2) domains are conserved among all members of the DKK family; B: Phylogenetic tree of the DKK proteins. Amino acid sequences were aligned by the Clustal W program, and the phylogenetic tree was constructed by the neighbour joining method. The scale bar indicates the estimated number of substitutions per 50 amino acids. SP: Signal peptide.