4rsc
Crystal structure of RPE65 in complex with emixustat and palmitate
Structural highlights
FunctionRPE65_BOVIN Plays important roles in the production of 11-cis retinal and in visual pigment regeneration. The soluble form binds vitamin A (all-trans-retinol), making it available for LRAT processing to all-trans-retinyl ester. The membrane form, palmitoylated by LRAT, binds all-trans-retinyl esters, making them available for IMH (isomerohydrolase) processing to all-cis-retinol. The soluble form is regenerated by transferring its palmitoyl groups onto 11-cis-retinol, a reaction catalyzed by LRAT. The enzymatic activity is linearly dependent of the expression levels and membrane association.[1] [2] [3] Publication Abstract from PubMedVisual function in vertebrates is dependent on the membrane-bound retinoid isomerase RPE65, an essential component of the retinoid cycle pathway that regenerates 11-cis-retinal for rod and cone opsins. The mechanism by which RPE65 catalyzes stereoselective retinoid isomerization has remained elusive because of uncertainty about how retinoids bind to its active site. Here we present crystal structures of RPE65 in complex with retinoid-mimetic compounds, one of which is in clinical trials for the treatment of age-related macular degeneration. The structures reveal the active site retinoid-binding cavity located near the membrane-interacting surface of the enzyme as well as an Fe-bound palmitate ligand positioned in an adjacent pocket. With the geometry of the RPE65-substrate complex clarified, we delineate a mechanism of catalysis that reconciles the extensive biochemical and structural research on this enzyme. These data provide molecular foundations for understanding a key process in vision and pharmacological inhibition of RPE65 with small molecules. Catalytic mechanism of a retinoid isomerase essential for vertebrate vision.,Kiser PD, Zhang J, Badiee M, Li Q, Shi W, Sui X, Golczak M, Tochtrop GP, Palczewski K Nat Chem Biol. 2015 Jun;11(6):409-15. doi: 10.1038/nchembio.1799. Epub 2015 Apr, 20. PMID:25894083[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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