Figure 1

Functional domains of 2DBD-Nuclear receptors and sequence alignment of the LBD domain. A. Schematic representation of functional domains of 2DBD-NRs isolated from the fluke Schistosoma mansoni. hRORα (human RAR-related orphan receptor, NM_002943) as an example that shows the 'typical' modular structure of nuclear receptors, which contain an A/B domain, a C domain (DNA binding domain), a D domain (hinge region) and an E domain (ligand binding domain). Three Sm2DBD NRs (Sm2DBDα, Sm2DBDβ and Sm2DBDγ) exhibit a novel modular structure with an AB domain, two tandem DNA binding domains (C1 and C2), a D domain and an E domain. Sm2DBDα possesses an F domain at the C-terminal end of the E domain. The size of each domain in amino acids is indicated. B. Alignment of sequences from Helices 3–12 of the LBD domain of three S. mansoni 2DBD-NRs with that of members in NR subfamily I. Helices described in [64] are boxed, the signature sequence of the LBD (Tτ) is boxed with dash line. The autonomous activation domain (AF2-AD) is indicated and the conserved glutamic acids are shown in bold. Numbers at the end of each line indicate residue positions in the original sequence, amino acids of Sm2DBDα 1371–1527 and hRARα 453–462 are not shown in the alignment. Dark shaded areas show conserved residues in the signature sequence of the LBD. The accession numbers of the aligned human nuclear receptors can be found in additional file 2.