Other unnatural amino acids contain photoaffinity labels and other "crosslinkers" that could be used for trapping proteinprotein interactions by forcing interacting proteins to be covalently attached to one another. Purifying these linked proteins would allow scientists to see what proteins interact with in living cells -- even those with weak interactions that are difficult to detect by current methods.
Unnatural amino acids are also important in medicine, and many proteins used therapeutically need to be modified with chemical groups such as polymers, crosslinking agents, and cytotoxic molecules. Last year, Schultz and his Scripps Research colleagues also showed that glycosylated amino acids could be incorporated site-specifically to make glycosylated proteins -- an important step in the preparation of some medicines.
Novel hydrophobic amino acids, heavy metal-binding amino acids, and amino acids that contain spin labels could be useful for probing the structures of proteins into which they are inserted. And unusual amino acids that contain chemical moieties like "keto" groups, which are like LEGO blocks, could be used to attach other chemicals such as sugar molecules, which would be relevant to the production of therapeutic proteins.
Combining Amber Suppression with Frame Shift Suppression
Schultz and his colleagues succeeded in making the 22-amino acid E. coli by exploiting the redundancy of the genetic code. When a protein is expressed, an enzyme reads the DNA bases of a gene (A, G, C, and T), and transcribes them into RNA (A, G, C, and U). This so-called "messenger RNA" is then translated by another protein-RNA complex, called the ri
Contact: Jason Bardi
Scripps Research Institute