Slowly improving
Rubisco, the most occurring enzyme of our planet, is not really efficient. It is more a good enough type of enzyme. Now researchers from England show that rubisco is one of the slowest evolving proteins, which is improving with each slow step it takes.
Rubisco, the enzyme that is converting CO2 into sugars, originated in a completely different word. One with lots of CO2 and hardly any O2 in its atmosphere. Now that is reversed, which is making rubisco also a lot less efficient. It often confuses O2 for CO2. But that is raising the question: Why hasn’t this so important enzyme not further evolved?
To answer this the researchers studied the rubisco gene sequences of 488 species. Rubisco is build from 4 large an 4 small subunits. With the larger subunits doing the conversion of CO2 into sugars and the smaller subunits keeping everything in the right shape. The researchers discovered less differences between the genes of the large subunits than between the small subunits.
Rubisco belongs to the 1.9% slowest evolving protein
The researches compared the speed at which the large rubisco subunits collected changes with that of other genes. They discovered that rubisco belonged to the 1.9% slowest evolving proteins of the world. Showing that rubisco is evolving, albeit verry slowly.
Subsequently the researchers studied the effect of this slow evolution. Hereby the researchers discovered that each long lasting change in the gene of the large rubisco subunit positively contributes to the efficiency of the enzyme.
The researchers think that rubisco is evolving slower than most proteins because it 1) needs to keep its functionality, and 2) its required interaction with companion proteins. So a change with a negative effect on one of those will likely has a drastic negative effect on the vitality of the organism. Resulting in extreme slow evolution.
Literature
Jacques W. Bouvier, David M. Emms, and Steven Kelly (2024) Rubisco is evolving for improved catalytic efficiency and CO2 assimilation in plants. PNAS, 121 (11) e2321050121, https://doi.org/10.1073/pnas.2321050121
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