Human Cellular Retinaldehyde-Binding Protein Has Secondary Thermal 9-cis-Retinal Isomerase Activity
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- 作者：Christin S. Bolze ; Rachel E. Helbling ; Robin L. Owen ; Arwen R. Pearson ; Guillaume Pompidor ; Florian Dworkowski ; Martin R. Fuchs ; Julien Furrer ; Marcin Golczak ; Krzysztof Palczewski ; Michele Cascella ; Achim Stocker
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：January 8, 2014
- 年：2014
- 卷：136
- 期：1
- 页码：137-146
- 全文大小：414K
- ISSN：1520-5126
文摘
Cellular retinaldehyde-binding protein (CRALBP) chaperones 11-cis-retinal to convert opsin receptor molecules into photosensitive retinoid pigments of the eye. We report a thermal secondary isomerase activity of CRALBP when bound to 9-cis-retinal. UV/vis and 1H NMR spectroscopy were used to characterize the product as 9,13-dicis-retinal. The X-ray structure of the CRALBP mutant R234W:9-cis-retinal complex at 1.9 脜 resolution revealed a niche in the binding pocket for 9-cis-aldehyde different from that reported for 11-cis-retinal. Combined computational, kinetic, and structural data lead us to propose an isomerization mechanism catalyzed by a network of buried waters. Our findings highlight a specific role of water molecules in both CRALBP-assisted specificity toward 9-cis-retinal and its thermal isomerase activity yielding 9,13-dicis-retinal. Kinetic data from two point mutants of CRALBP support an essential role of Glu202 as the initial proton donor in this isomerization reaction.