Figure 2.

There is a single ER in amphioxus. (A) Schematic representation of the different domains of amphiER. Percent identity of the amphioxus ER with other sequences from the NR3 subfamily in the DNA- and ligand-binding domains is indicated. Amino acid sequence of the highly conserved P-box and D-box in the DBD are shown. (B) Maximum likelihood (ML) tree obtained from the analysis of the amino acid sequences of the DBD and the LBD of a wide range of NR3 under a JTT+γ +i model. Bootstrap percentages obtained after 1,000 ML replicates are shown above selected branches. Scale bar indicates number of changes per site. The tree was rooted by selected RXR sequences. (C) The exon-intron structure of amphiER is conserved with that of human ERα, except two minor differences: the first human exon corresponds to the first two amphioxus exons and the last two human exons correspond to the last amphioxus exon.