Researchers Find Way to Supercharge Protein Production

Even though scientists have engineered bacteria to make therapeutic proteins, medicines based on these proteins, such as insulin and clotting factors for hemophilia, are still difficult to synthesize in the lab. Now, through the use of green fluorescent protein, researchers at Washington University School of Medicine have found a way to supercharge protein production a thousandfold. The discovery resulted from an experiment that turned out differently than expected.

While investigating how to control the amount of protein produced from a specific gene, professor Sergej Djuranovic and researcher Manasvi Verma experimented with changing the sequence of the first few amino acids of a protein. “We thought it would have no effect on protein expression, but instead, it increased protein expression by 300%,” Djuranovic said. “So then we started digging in to why that happened.”

The researchers turned to green fluorescent protein, a tool used in biomedical research to estimate the amount of protein in a sample by measuring the amount of fluorescent light produced. The researchers randomly changed the sequence of the first few amino acids in green fluorescent protein, generating 9261 distinct versions, identical except for the very beginning.

Tubes of green fluorescent protein glow more brightly when they contain more of the protein. Researchers at Washington University School of Medicine have found a way to increase protein production up to one thousandfold, a discovery that could aid production of proteins used in the medical, food, agriculture, chemical, and other industries. Courtesy of Sergej Djuranovic.

The brilliance of the different versions of green fluorescent protein varied thousandfold from the dimmest to the brightest, indicating a thousandfold difference in the amount of protein produced. With careful analysis and further experiments, the researchers from Washington University and their colleagues from Stanford University identified certain combinations of amino acids at the third, fourth, and fifth positions in the protein chain that gave rise to very large amounts of protein.

Moreover, they found that the same amino-acid triplets not only ramped up production of green fluorescent protein, which originally comes from jellyfish, but also production of proteins from distantly related species like coral and humans. “This technique works with all kinds of proteins because it’s a basic feature of the universal protein-synthesizing machinery,” Djuranovic said.

The findings could help increase production of proteins not only for medical applications, but in food, agriculture, chemical, and other industries. “If you can make each bacterium produce 10 times as much protein, you only need one-tenth the volume of bacteria to get the job done, which would cut costs tremendously,” Djuranovic said.

“There are so many ways we could benefit from ramping up protein production. In the biomedical space, there are many proteins used in drugs, vaccines, diagnostics, and biomaterials for medical devices that might become less expensive if we could improve production.”

The research was published in Nature Communications (www.doi.org/10.1038/s41467-019-13810-1).