Type I and type II rhodopsins share several structural features including a G protein-coupled receptor fold and a highly conserved active-site Lys residue in the seventh transmembrane segment of the protein. However, the two families lack significant sequence similarity that would indicate common ancestry. Consequently, the rhodopsin fold and conserved Lys are widely thought to have arisen from functional constraints during convergent evolution. To test for the existence of such a constraint, we asked whether it were possible to relocate the highly conserved Lys296 in the visual pigment bovine rhodopsin. We show here that the Lys can be moved to three other locations in the protein while maintaining the ability to form a pigment with 11-cis-retinal and activate the G protein transducin in a light-dependent manner. These results contradict the convergent hypothesis and support the homology of type I and type II rhodopsins by divergent evolution from a common ancestral protein.
This research output has an Altmetric Attention Score of 5. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 30 November 2025.
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#9,597,966
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Outputs from Proceedings of the National Academy of Sciences of the United States of America
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Outputs of similar age from Proceedings of the National Academy of Sciences of the United States of America
#592
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Altmetric has tracked 34,357,314 research outputs across all sources so far. This one has received more attention than most of these and is in the 70th percentile.
So far Altmetric has tracked 118,924 research outputs from this source. They typically receive a lot more attention than average, with a mean Attention Score of 40.1. This one is in the 35th percentile – i.e., 35% of its peers scored the same or lower than it.
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We're also able to compare this research output to 917 others from the same source and published within six weeks on either side of this one. This one is in the 33rd percentile – i.e., 33% of its contemporaries scored the same or lower than it.
