SmRXR and SmRXR2 are two recently discovered nuclear receptors in S. mansoni which resembles in sequence the retinoid x receptor (RXR). They are the largest known members of the RXR family: SmRXR is a 74kDa protein, while SmRXR-2 weighs 78kDa. Phylogenetic analysis supports that SmRXR2 is the most ancient full-length RXR identified. The sequences of their LBDs show low conservation when compared to human RXRs. In this work, we have constructed homology models of SmRXR and SmRXR2 in order to analyse its possible interactions with ligands. These models were constructed using the software Modeller and validated using the softwares Procheck, Whatcheck and Verify3D. We have used both apo and holo structures of RXR as templates for our models, in order to scrutinize the putative ligand binding sites on the S. mansoni nuclear receptors. Our analysis favours  the hypothesis that SmRXR1 and SmRXR2 may bind different ligands, and also that the binding of 9-cis retinoic acid, the endogenous ligand of human RXR, is unlikely for SmRXR2.

References:
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