(A and B) The conservation of the tammar HOXA13 (A) and HOXD13 (B) protein sequence. Tammar protein is compared with human, mouse, opossum, bat and chicken orthologues. Shaded boxes show conservation of amino acids and crosses represent gaps in the sequence. Polyalanine tracts (red outline), polyserine tracts (green outline), homeodomains (blue outline) and HOXA13_N superfamily (black outline) are indicated by the boxed outlines. HOXD13 alignment of both tammar and opossum showed that the first polyserine repeats are missing in the tammar and the amino acids in this region differ markedly from the other 5 species shown (Figure 4B highlighted in yellow). Comparison of HOXD13 N-terminal secondary structure of this region (Figure 4C) showed that tammar produced a 13 α-helix structure (labelled with black frame) but the opossum and human only possess a 3 α-helix in the same region. Tammar, opossum and human all share a highly conserved α-helix structure (indicated by the red frame). Additionally another α-helix structure is present in tammar and opossum, but is absent in human (indicated by the black frame).
Chew et al. BMC Developmental Biology 2012 12:2 doi:10.1186/1471-213X-12-2