If you’ve ever been stuck wrestling a jar lid that just won’t budge, you already know what plants go through with Rubisco. It’s the enzyme that’s supposed to help them turn sunlight into food — and yet it plods along like it’s on a coffee break. To make matters worse, it has a habit of grabbing oxygen instead of carbon dioxide, which is about as useful as putting salt in your coffee.
That flaw has bugged scientists for decades. Now, a team at MIT says it’s managed to make a bacterial version of Rubisco up to 25% more efficient. According to MIT News, the fix stems from a technique called continuous directed evolution — basically a way of nudging nature to run trial-and-error at hyperspeed, all inside living cells instead of in a test tube. The research was published in the Proceedings of the National Academy of Sciences.
“This is, I think, a compelling demonstration of successful improvement of a Rubisco’s enzymatic properties, holding out a lot of hope for engineering other forms of Rubisco,” said MIT chemistry professor Matthew Shoulders. He and research scientist Robert Wilson worked alongside lead author Julie McDonald to make the breakthrough.
Rubisco’s job is to grab carbon from CO2 and start turning it into sugars. The trouble is it’s slow — sometimes just one reaction a second — and it misfires when oxygen gets in the way, wasting energy plants could use to grow. McDonald called that “a really attractive set of problems” for protein engineers, the kind that can be tackled by tweaking the enzyme’s amino acids.
The team’s new method, called MutaT7, pushes mutation rates much higher than older approaches. Because the changes happen inside the cell, scientists can quickly keep the winners and toss the losers. After six rounds of mutating Rubisco from Gallionellaceae bacteria, they landed on three changes near the enzyme’s active site. Those tweaks made it less likely to react with oxygen, which boosted its ability to grab carbon dioxide.
“The underlying question here is: Can you alter and improve the kinetic properties of Rubisco to operate better in environments where you want it to operate better?” Shoulders said. For this strain, at least, the answer is looking like yes.
Next up: testing it in plant-based Rubisco. Wilson said plants can lose around 30% of their captured sunlight energy to photorespiration, which happens when Rubisco mistakes oxygen for carbon dioxide. Cutting that waste could mean higher yields and sturdier crops in a warming climate. Genetic tweaks in other plants, such as poplar trees, have also shown promising results for growth and biomass. Bacteria-based structures called carboxysomes have been studied for their ability to boost plant growth as well.
“This really opens the door to a lot of exciting new research,” Wilson said, adding that better Rubisco could lead to “definite benefits to agricultural productivity.”
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