New protein speeds up biofuel production

For this research, Gonzalez-Esquer worked with Cheryl Kerfeld, the Hannah Distinguished Professor of Structural Bioengineering in the Michigan State University-DOE Plant Research Lab, and Tyler Shubitowski, MSU undergraduate student. Kerfield’s lab studies bacterial microcompartments, or BMCs. These are self-assembling cellular organs that perform myriad metabolic functions, and in a sense, they are molecular factories with many different pieces of machinery.

They modernized the factory by updating the carboxysome, a particularly complex BMC that requires a series of protein-protein interactions involving at least six gene products to form a metabolic core that takes CO₂ out of the atmosphere and converts it into sugar. To streamline this process, the team created a hybrid protein in cyanobacteria, organisms that have many potential uses for making green chemicals or biofuels.

The new protein replaces four gene products, yet still supports photosynthesis. Reducing the number of genes needed to build carboxysomes should facilitate the transfer of carboxysomes into plants.

This installation should help plants’ ability to fix carbon dioxide. Improving their capacity to remove CO₂ from the atmosphere makes it a win-win, Gonzalez-Esquer said.

“It’s comparable to making coffee. Rather than getting an oven to roast the coffee beans, a grinder to process them and a brewing machine, we’ve built a single coffeemaker where it all happens in one place,” he said. “The new tool takes raw material and produces the finished product with a smaller investment.”

However, this altered cyanobacterial species won’t be taking over any ponds, or the world, anytime soon. While the improved organisms excel at photosynthesis in a lab setting, they’re ill prepared to compete with other bacteria. Because they were stripped of four genes, they’re not as flexible as their natural cousins.