| Thermal properties of rhodopsin: Insight into the molecular mechanism of dim-light vision. | |
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MedLine Citation:
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PMID: 21659526 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Rhodopsin has developed mechanisms to optimize its sensitivity to light by suppressing dark noise and enhancing quantum yield. We propose that an intramolecular hydrogen-bonding network formed by ~20 water molecules, the hydrophilic residues, and peptide backbones in the transmembrane region is essential to restrain thermal isomerization, the source of dark noise. We studied the thermal stability of rhodopsin at 55 degree C with single point mutations, E181Q and S186A, that perturb the hydrogen-bonding network at the active site. We found that the rate of thermal isomerization increases by 1-2 orders of magnitude in the mutants. Our results illustrate the importance of the intact hydrogen-bonding network for dim-light detection, revealing the functional roles of water molecules in rhodopsin. We also showed that thermal isomerization of 11-cis retinal in solution can be catalyzed by wild-type opsin and that this catalytic property is not affected by the mutations. We characterize the catalytic effect and propose it is due to steric interactions in the retinal binding site and increases quantum yield by predetermining the trajectory of photoisomerization. Thus, our studies reveal a balancing act between dark noise and quantum yield, which have opposite effects on thermal isomerization rate. The acquisition of the hydrogen-bonding network and the tuning of the steric interactions at the retinal binding site are two important factors in the development of dim-light vision. |
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Authors:
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Jian Liu; Monica Yun Liu; Jennifer B Nguyen; Aditi Bhagat; Victoria Mooney; Elsa C Y Yan |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-6-9 |
Journal Detail:
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Title: The Journal of biological chemistry Volume: - ISSN: 1083-351X ISO Abbreviation: - Publication Date: 2011 Jun |
Date Detail:
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Created Date: 2011-6-10 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985121R Medline TA: J Biol Chem Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Yale University, United States. |
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