La Jolla, CA Researchers at the Salk Institute for Biological Studies have developed a novel strategy to expand the natural repertoire of 20 amino acids in mammalian cells, including neurons, and successfully inserted tailor-made amino acids into proteins in these cells. In a powerful demonstration of the methods versatility, they then used unnatural amino acids to determine the operating mechanism of the molecular gates that regulate the movement of potassium ions in and out of nerve cells.
In the past, this type of engineering has been mainly restricted to bacteria or in yeast, and it was very challenging to efficiently incorporate unnatural amino acids in mammalian cells. But most biomedical questions have to be studied in the cells of higher organisms and animal models to arrive at meaningful answers, explains Lei Wang, Ph.D., an assistant professor in the Chemical Biology and Proteomics Laboratory, who led the current study published in the July issue of Nature Neuroscience.
The genetic code, which is shared by plants, animals and bacteria, includes 64 codons encoding 20 different amino acids and three stop signals. Being able to expand the code and insert non-natural amino not only greatly enhances researchers' ability and precision, but also provides novel tools for addressing challenging questions insurmountable with conventional means.
We had tried using conventional mutagenesis to introduce mutations into the potassium channel but it didnt give us any answers, says Paul A. Slesinger, Ph.D., an associate professor in the Peptide Biology Laboratory, who collaborated with Wang on the current study. Being able to incorporate bulky unnatural amino acids into living mammalian cells really made all the difference, he adds.
During his graduate studies, Wang pioneered a method to accommodate additional amino acids in bacteria. His approach mimicked the strategy every cell relies on to incorporate conventional amino acids
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