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The Gluopsins: Opsins without the Retinal Binding Lysine
Martin Gühmann1, Megan L Porter2, Michael J Bok3
1School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK.
Cells
|August 12, 2022
Summary
Researchers discovered novel opsins, termed gluopsins, that have lost a key lysine residue essential for light detection. These gluopsins, found in insects, may have alternative functions beyond photoreception, expanding our understanding of opsin evolution.
Area of Science:
- Evolutionary Biology
- Molecular Biology
- Biochemistry
Background:
- Opsins are G-protein-coupled receptors crucial for vision, typically binding retinal via a conserved lysine residue.
- This conserved lysine is a defining feature for opsin identification and phylogenetic analysis.
- Recent findings suggest some opsins function as chemoreceptors, where the lysine is not essential.
Purpose of the Study:
- To investigate the existence of opsins that have lost the conserved lysine residue during evolution.
- To construct a comprehensive opsin phylogeny to identify such divergent opsins.
Main Methods:
- Development of an automated pipeline for compiling, aligning, and reconstructing large-scale opsin phylogenies.
- Phylogenetic analysis of public sequence data to identify opsin clades.
- Sequence analysis to characterize conserved motifs and identify lysine replacements.
Main Results:
- Construction of the largest opsin phylogeny to date, encompassing 4956 opsin sequences.
- Identification of a novel clade of 33 opsins, named 'gluopsins', characterized by glutamic acid replacing the conserved lysine.
- Gluopsins are predominantly found in dragonflies and butterflies and are phylogenetically related to RGR-opsins and retinochromes, sharing a derived NPxxY motif.
Conclusions:
- The discovery of gluopsins challenges the traditional definition of opsins based on the conserved lysine.
- Gluopsins represent a significant evolutionary divergence, suggesting potential non-photoreceptive functions.
- Further research is needed to elucidate the specific functions of these newly identified gluopsins.
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