Undergrads find improved antifreeze in beetles

A team of Yale undergraduates has discovered the structure of of the most powerful known antifreeze to date.

The researchers investigated an antifreeze protein found in Siberian beetles, which survive winters with temperatures dipping as low as -40 degrees Fahrenheit. They found that the protein’s flat molecular structure allows it to bind to ice crystals in a way that prevents their growth hundreds of times more effectively than can salt and other common de-icers. Originally published online by the Journal of Biological Chemistry in March, the study will make the cover of the journal’s April 26 issue.

The findings stemmed from a research project the team submitted to the 2011 International Genetically Engineered Machines (iGEM) Competition, in which teams of synthetic biology undergraduate researchers worldwide manipulate genetically engineered E. coli bacteria to construct new biological systems. Earlier that year, Aaron Hakim ’13, a co-lead author of the study, had read about prior research describing the highly potent antifreeze in the Siberian beetle — known as Rhagium inquisitor or the ribbed pine borer.

“It’s one of the most active antifreeze proteins, if not the most. And it has the largest ice-binding site currently known,” said co-lead author Jennifer Nguyen GRD ’14. “We were able to determine its 3-D structure.”

The undergraduates copied the gene that corresponds to the antifreeze protein in the beetle and expressed it in E. coli bacteria, which produced large quantities of the protein. Senior author Wuyi Meng, a research support specialist at Yale in the Chemical and Biophysical Instrumentation Center, then helped the team visualize and analyze the protein structure, revealing an unusually flat surface that allows it to inhibit ice formation. Nguyen said the team could see water molecules perfectly lodged in the grooves of the protein, and observed how the layers of water molecules interacted with ice crystals to prevent their growth. Meng added that the precise mechanism by which the protein binds to the ice is still unclear.

Meng and Nguyen said these antifreeze proteins could potentially be used to improve the consistency of ice cream, to preserve transplant organs or embryos stored at fertility clinics, and to engineer frost resistance in crops, among other applications.

The study made the Yale team a regional finalist for the Americas in the 2011 iGEM competition. Now, Nguyen said Hakim is trying to engineer the structure of the protein to see if they can improve its efficiency.

The undergraduates were supervised by Farren Isaacs, an assistant professor of molecular, cellular and developmental biology.