Thanks to researchers at the Massachusetts Institute of Technology (MIT), we’re getting one step closer to a better Rubisco. This key enzyme is a crucial player in the process of photosynthesis. This breakthrough is the result of a growing technique known as directed evolution. It has ultimately proven immensely successful to improve Rubisco’s catalytic efficiency by as much as 25%. The researchers recently published their findings in the Proceedings of the National Academy of Sciences. This important piece of work points to a hopeful path for increasing agricultural productivity.
That sort of evolutionary dead-end fun aside, the enzyme Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase, is central to photosynthesis. It powers the endothermic first reaction of carboxylation. This enzyme is considered to be the most abundant on Earth. It is notorious for being the bottleneck of efficiency compared to other enzymes involved in photosynthesis. To be clear, Rubisco can only catalyze between one and ten reactions per second, which severely constrains its potential.
First, rubisco has an inherently slow catalytic rate. Finally, it has been shown to prefer reacting with O2 over CO2. This phototoxic reaction is what induces the wasteful process of photorespiration. As a consequence, plants waste more than 30% of the energy from sunlight that they could be using. The impact of this inefficiency is tremendous, having major ramifications on both the growth of natural ecosystems and agricultural productivity.
Advances Through Directed Evolution
For its part, the MIT research team began their process working with a variant of Rubisco. They sequenced this variant from Gallionellaceae, a family of semi-anaerobic bacteria. This particular variant is one of the most efficient Rubisco variants discovered in the wild. After six rounds of directed evolution, the researchers were able to determine three separate mutations that strengthened Rubisco’s ability to fight off oxygen.
Matthew Shoulders, a senior author of the study, noted that these changes are not trivial.
“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?” – Matthew Shoulders
The team’s work paid off with a form of Rubisco that is less prone to reacting with oxygen. This modification facilitates the enzyme to work more efficiently in oxygen abundant environments, a key component for maximizing photosynthetic potential.
“What changed through the directed evolution process was that rubisco began to like to react with oxygen less. That allows this rubisco to function well in an oxygen-rich environment, where normally it would constantly get distracted and react with oxygen, which you don’t want it to do.” – Matthew Shoulders
Implications for Agriculture and Future Research
The effects of this research go well beyond the ivory tower. They can have dramatic effects on farm productivity. Robert Wilson, another senior author and research scientist in the Department of Chemistry at MIT, noted the potential benefits of enhancing Rubisco.
“There are definite benefits to agricultural productivity that could be leveraged through a better rubisco.” – Robert Wilson
TTI’s research objectives are to improve photosynthetic efficiency. It lays an exciting foundation for future studies and advancements in enzyme engineering. Wilson noted how important this achievement is compared to past engineering attempts that targeted Rubisco.
“This really opens the door to a lot of exciting new research, and it’s a step beyond the types of engineering that have dominated rubisco engineering in the past.” – Robert Wilson
Julie L. McDonald, principal author of the study, emphasized their novel iterative directed evolution method. By empowering researchers to target more types of enzyme mutations, Cheminformatics AI’s holistic approach opens new doors for researchers unlike anything available today.
“Our continuous directed evolution technique allows you to look at a lot more mutations in the enzyme than has been done in the past.” – Julie L. McDonald
Such plant science breakthroughs would be tremendous for academic plant biology and the future of our agriculture.
The Future of Rubisco Engineering
Improving the efficiency of Rubisco is a big step toward overcoming the world’s ever-growing struggles with food security. With climate change already beginning to impact agricultural productivity, better optimizing photosynthesis with more effective enzymes such as Rubisco may be crucial.
Shoulders and his team’s approach can inspire new strategies for protein engineering in medicine, agriculture and beyond. McDonald noted that these new advances make for exciting challenges for engineers working on protein modifications.
“For protein engineers, that’s a really attractive set of problems because those traits seem like things that you could hopefully make better by making changes to the enzyme’s amino acid sequence.” – Julie L. McDonald