Retinol-Binding Site in Interphotoreceptor Retinoid-Binding Protein (IRBP): A Novel Hydrophobic Cavity

摘要

PurposeInterphotoreceptor retinoid-binding protein (IRBP) appears to target and protect retinoids during the visual cycle. X-ray crystallographic studies had noted a ββα-spiral fold shared with crotonases and C-terminal protein transferases. The shallow cleft formed by the fold was assumed to represent the retinol-binding site. However, a second hydrophobic site consisting of a highly restricted cavity was more recently appreciated during in silico ligand-docking studies. In this study, the ligand-binding environment within the second module of Xenopus IRBP (X2IRBP) is defined.