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Author Notes:
Correspondence: S. Yokoyama; Tel.: +1 404 727 5379; Fax: +1 404 727 288; Email: syokoya@emory.edu
Acknowledgments: We thank Drs. K. Morokuma, K. Ohmiya, R. Yokoyama, and anonymous reviewers for their comments on the manuscript.
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Research Funding:
This work was supported by a grant from the National Institutes of Health and start-up fund from Emory University.
Keywords:
- Visual pigments
- Crystal structure
- UV vision
- Violet vision
- Vertebrates
Tertiary structure and spectral tuning of UV and violet pigments in vertebrates
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Abstract:
Many vertebrate species use ultraviolet (UV) vision for such behaviors as mating, foraging, and communication. UV vision is mediated by UV-sensitive visual pigments, which have the wavelengths of maximal absorption (λmax) at ~360 nm, whereas violet (or blue) vision is mediated by orthologous pigments with λmax values of 390–440 nm. It is widely believed that amino acids in transmembrane (TM) I–III are solely responsible for the spectral tuning of these SWS1 pigments. Recent molecular analyses of SWS1 pigments, however, show that amino acids in TM IV–VII are also involved in the spectral tuning of these pigments through synergistic interactions with those in TM I–III. Comparisons of the tertiary structures of UV and violet pigments reveal that the distance between the counterion E113 in TM III and amino acid sites 87–93 in TM II is narrower for UV pigments than for violet pigments, which may restrict the access of water molecules to the Schiff base pocket and deprotonate the Schiff base nitrogen. Both mutagenesis analyses of E113Q and quantum chemical calculations strongly suggest that unprotonated Schiff base-linked chromophore is responsible for detecting UV light.
Copyright information:
© 2005 Elsevier B.V. All rights reserved.
This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).
