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Opsin phylogeny and evolution: a model for blue shifts in wavelength regulation.
Mol Phylogenet Evol. 1995 Mar; 4(1):31-43.MP

Abstract

The vast diversity in spectral sensitivities in the vision of many organisms is mediated mostly (although not entirely) through variation in the photosensitive visual pigments (opsins) of the eye. Specifically, shifts in absorption maxima of visual pigments are thought to be a result of interactions within the binding pocket of the opsin, between amino acid side chains and the retinal chromophore, However, it has proven difficult to identify specific amino acid residues important in determining wavelength absorption maxima, especially for some of the short wavelength (blue) opsins. In this paper, a comparative phylogenetic approach was applied to opsin protein sequence data to identify residues important in opsin wavelength regulation. In essence, this approach consisted of interpreting evolutionary history as a series of experiments in which natural selection has repeatedly favored amino acid replacements of certain residues to shift the opsin absorption spectra to either shorter or longer wavelengths. Opsin protein sequences were obtained from GenBank, aligned, and used to reconstruct a phylogenetic tree. Amino acid replacements were traced along the branches of this opsin tree, focusing only on residues likely to reside within the chromophore-binding pocket. A number of functionally convergent, nonconservative amino acid replacements in independently evolved opsins with similar shifts in spectral properties were identified. In short, reconstruction of the phylogeny of the opsin molecule allowed us to track amino acid substitutions in specific sites within the opsin and to target those particular substitutions that are repeatedly associated with marked changes in peak absorbance, shifting the spectral sensitivity of the opsin toward shorter or longer wavelengths. Based on these results, we propose a model for blue shifts of opsin absorption spectra. Amino acid replacements of four polar and charged residues near the protonated Schiff base (SBH+) end of the chromophore are proposed to result in blue shifts of the opsin absorption spectra. This model may explain some of the diversity of blue opsins apparent in both vertebrates and invertebrates.

Authors+Show Affiliations

Program in Neuroscience, Harvard University, Cambridge, Massachusetts 02138, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

7620634

Citation

Chang, B S., et al. "Opsin Phylogeny and Evolution: a Model for Blue Shifts in Wavelength Regulation." Molecular Phylogenetics and Evolution, vol. 4, no. 1, 1995, pp. 31-43.
Chang BS, Crandall KA, Carulli JP, et al. Opsin phylogeny and evolution: a model for blue shifts in wavelength regulation. Mol Phylogenet Evol. 1995;4(1):31-43.
Chang, B. S., Crandall, K. A., Carulli, J. P., & Hartl, D. L. (1995). Opsin phylogeny and evolution: a model for blue shifts in wavelength regulation. Molecular Phylogenetics and Evolution, 4(1), 31-43.
Chang BS, et al. Opsin Phylogeny and Evolution: a Model for Blue Shifts in Wavelength Regulation. Mol Phylogenet Evol. 1995;4(1):31-43. PubMed PMID: 7620634.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Opsin phylogeny and evolution: a model for blue shifts in wavelength regulation. AU - Chang,B S, AU - Crandall,K A, AU - Carulli,J P, AU - Hartl,D L, PY - 1995/3/1/pubmed PY - 1995/3/1/medline PY - 1995/3/1/entrez SP - 31 EP - 43 JF - Molecular phylogenetics and evolution JO - Mol Phylogenet Evol VL - 4 IS - 1 N2 - The vast diversity in spectral sensitivities in the vision of many organisms is mediated mostly (although not entirely) through variation in the photosensitive visual pigments (opsins) of the eye. Specifically, shifts in absorption maxima of visual pigments are thought to be a result of interactions within the binding pocket of the opsin, between amino acid side chains and the retinal chromophore, However, it has proven difficult to identify specific amino acid residues important in determining wavelength absorption maxima, especially for some of the short wavelength (blue) opsins. In this paper, a comparative phylogenetic approach was applied to opsin protein sequence data to identify residues important in opsin wavelength regulation. In essence, this approach consisted of interpreting evolutionary history as a series of experiments in which natural selection has repeatedly favored amino acid replacements of certain residues to shift the opsin absorption spectra to either shorter or longer wavelengths. Opsin protein sequences were obtained from GenBank, aligned, and used to reconstruct a phylogenetic tree. Amino acid replacements were traced along the branches of this opsin tree, focusing only on residues likely to reside within the chromophore-binding pocket. A number of functionally convergent, nonconservative amino acid replacements in independently evolved opsins with similar shifts in spectral properties were identified. In short, reconstruction of the phylogeny of the opsin molecule allowed us to track amino acid substitutions in specific sites within the opsin and to target those particular substitutions that are repeatedly associated with marked changes in peak absorbance, shifting the spectral sensitivity of the opsin toward shorter or longer wavelengths. Based on these results, we propose a model for blue shifts of opsin absorption spectra. Amino acid replacements of four polar and charged residues near the protonated Schiff base (SBH+) end of the chromophore are proposed to result in blue shifts of the opsin absorption spectra. This model may explain some of the diversity of blue opsins apparent in both vertebrates and invertebrates. SN - 1055-7903 UR - https://www.unboundmedicine.com/medline/citation/7620634/Opsin_phylogeny_and_evolution:_a_model_for_blue_shifts_in_wavelength_regulation_ DB - PRIME DP - Unbound Medicine ER -