Evolution: the newly-found bacterial role: (Evolution)

by David Turell , Monday, August 31, 2020, 20:21 (1543 days ago) @ David Turell

An enzyme that has been fixing inorganic carbon for billion s of years:

https://phys.org/news/2020-08-link-evolutionary-history-carbon-fixing-protein.html

"A team led by researchers at the University of California, Davis, has discovered a missing link in the evolution of photosynthesis and carbon fixation. Dating back more than 2.4 billion years, a newly discovered form of the plant enzyme rubisco could give new insight into plant evolution and breeding.

"Rubisco is the most abundant enzyme on the planet. Present in plants, cyanobacteria (also known as blue-green algae) and other photosynthetic organisms, it's central to the process of carbon fixation and is one of Earth's oldest carbon-fixing enzymes.

"'It's the primary driver for producing food, so it can take CO2 from the atmosphere and fix that into sugar for plants and other photosynthetic organisms to use. It's the primary driving enzyme for feeding carbon into life that way," said Doug Banda, a postdoctoral scholar in the lab of Patrick Shih, assistant professor of plant biology in the UC Davis College of Biological Sciences.

"Form I rubisco evolved over 2.4 billion years ago before the Great Oxygenation Event, when cyanobacteria transformed the Earth's atmosphere by producing oxygen through photosynthesis. Rubisco's ties to this ancient event make it important to scientists studying the evolution of life.

"In a study appearing Aug. 31 in Nature Plants, Banda and researchers from UC Davis, UC Berkeley and the Lawrence Berkeley National Laboratory report the discovery of a previously unknown relative of form I rubisco, one that they suspect diverged from form I rubisco prior to the evolution of cyanobacteria.

"The new version, called form I-prime rubisco, was found through genome sequencing of environmental samples and synthesized in the lab. Form I-prime rubisco gives researchers new insights into the structural evolution of form I rubisco, potentially providing clues as to how this enzyme changed the planet.

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"Form I rubisco is built from eight core large molecular subunits with eight small subunits perched on top and bottom. Each piece of the structure is important to photosynthesis and carbon fixation. Like form I rubisco, form I-prime rubisco is built from eight large subunits. However, it does not possess the small subunits previously thought essential.

"'The discovery of an octameric rubisco that forms without small subunits allows us to ask evolutionary questions about what life would've looked like without the functionality imparted by small subunits," said Banda. "Specifically, we found that form I-prime enzymes had to evolve fortified interactions in the absence of small subunits, which enabled structural stability in a time when Earth's atmosphere was rapidly changing."

"According to the researchers, form I-prime rubisco represents a missing link in evolutionary history. Since form I rubisco converts inorganic carbon into plant biomass, further research on its structure and functionality could lead to innovations in agriculture production."

Comment: Once again a study into enzymes, giant molecules that are especially adept at driving important reactions and because of their size require design.