Comment on Why photosynthetic organisms evolved to have dimeric reaction centres
sj_zero@lotide.fbxl.net 2 years ago
I'm interested to know how we know what chlorophyll was like billions of years ago. Seems like a chemical composition that would decompose over the course of even thousands of years.
Sal@mander.xyz 2 years ago
We don't know what chlorophyll was like billions of years ago! But we do know from studies on protein evolution the general paths that proteins take as they evolve, and it is highly likely that a structure as complex as these reaction center dimers began as a monomers and evolved to dimerize. The reason is that molecular evolution takes place in small steps, and evolving a complex structure while simultaneously maintaining its ability to form functional dimers as it evolves is not a likely pathway, because many mutation requires two functional changes (new functionality + self-interactions created or maintained). Furthermore, if there was no selective pressure to dimerize we would see today functional monomers being used as well. But we clearly see dimers, so there is clearly a strong evolutionary pressure, making it even more likely that these proteins evolved to dimerize. I recommend the book "Protein Evolution" by Laszlo Patthy for a technical overview on the topic, and many very cool and concrete examples.
In the paper they do explicitly point out our lack of knowledge about the past:
They also make many more specific claims about the evolutionary pathways and their logic, so if you are interested I recommend reading the "Evolutionary background" section of the original paper: https://pubs.rsc.org/en/content/articlepdf/2019/sc/c9sc03712h