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Rhodopsins from three frog and toad species: sequences and functional comparisons
N Fyhrquist1, K Donner, P A Hargrave
1Department of Biosciences, University of Helsinki, Helsinki, Finland.
Experimental Eye Research
|June 17, 1998
Summary
Bullfrog rhodopsin exhibits fewer thermal dark events than toad rhodopsin, despite similar light absorption. Researchers identified specific amino acid substitutions in Rana species potentially linked to this thermal stability difference.
Area of Science:
- Biochemistry
- Molecular Biology
- Vision Science
Background:
- Rhodopsin, a key visual pigment, exhibits thermal 'dark events' impacting rod cell function.
- Bullfrog rhodopsin shows a lower frequency of these events compared to certain toad species, despite similar spectral properties.
Purpose of the Study:
- To investigate amino acid substitutions potentially responsible for thermal stability differences in frog and toad rhodopsins.
- To identify specific molecular variations within the genus Rana and related anurans.
Main Methods:
- Sequencing of cDNA encoding rhodopsins from Bufo bufo, Bufo marinus, and Rana temporaria.
- Alignment of translated protein sequences with previously characterized rhodopsins from Rana catesbeiana, Rana pipiens, and Xenopus laevis.
Main Results:
- Sixteen non-conserved amino acid substitutions and six hydroxyl group gain/loss changes were identified across six anuran species.
- Specific substitutions unique to Rana (Ser/Thr at 220, Phe at 270) and Bufo (Phe at 274) were noted.
- Amino acids not cumulatively affecting absorbance characteristics were also identified.
Conclusions:
- A list of candidate amino acid substitutions for future thermal stability studies has been generated.
- Key residues potentially influencing rhodopsin thermal stability in anurans have been identified.