PULLMAN, Wash. — In the brave new world of industrial genetics, a major obstacle has been that the high temperatures needed for commercial production destroy the proteins that make the system work. Now,
Their process could lead to the rapid development of “designer” proteins such as pollution-degrading enzymes and anticancer agents. Their research is reported in a paper published May 6 in the prestigious journal Science.
Designer proteins are customized versions of naturally occurring proteins. Just as a van owner might add a biodiesel engine or a GPS system to the vehicle, a molecular biologist can modify a protein to make it perform in ways the original protein did not.
Black and her colleagues customized a protein to make it work at a higher temperature than it normally would, thus enhancing its potential to fight cancer. They did it through “computational design,” the use of a computer program that let them target specific parts of the protein and make only those changes most likely to create the effect they wanted.
According to Black, an associate professor in WSU’s Department of Pharmaceutical Sciences, computational design could cut years off the time needed to make useful new versions of a protein.
Until now, designer proteins were made by a labor-intensive process of creating mutations in the original protein and then screening them to find one that might be useful. Improving a protein’s thermal stability has been especially difficult because there has been no way of knowing what part of the protein to change. Most investigators make mutations in the active site or “business end” of the protein in order to alter how the enzyme works.
Black and her colleagues wanted to increase the enzyme’s stability at high temperatures, without changing its activity. Computational design let them protect the active site while altering other features.
The protein they worked with is an enzyme called yeast cytosine deaminase or yCD. Black has studied yCD for years because of its potential as a cancer therapy. One of her toughest challenges has been its preference for cool temperatures. The native form of yCD doesn’t work well at human body temperature. The form of yCD created through computational design works as well at 98.6 degrees as it does at room temperature. It also has a shelf-life 30 times longer than that of the native protein.
Black’s co-author Barry Stoddard of the
“It’s been an amazing project,” Black said. She is now testing the customized yCD for its ability to kill rat tumor cells.
The paper, “Computational Thermostabilization of an Enzyme,” was authored by Aaron Korkegian, Margaret E. Black, David Baker and Barry L. Stoddard. The research was funded by the National Institutes of Health.
