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Media Contact:
Dr. Alex Deiters, 919/513-2958
Tracey Peake, News Services, 919/515-6142

June 27, 2006

Researchers Create Genetically Coded Fluorescent Amino Acid, Lighting the Way to Study Proteins


A group of scientists, including a researcher at North Carolina State University, has discovered a more efficient way to create fluorescently labeled proteins that will aid in biomedical research.

Dr. Alex Deiters, assistant professor of chemistry in NC State’s College of Physical and Mathematical Sciences, assisted colleagues from the The Scripps Research Institute in his postdoctoral work. The researchers’ findings appear online in Proceedings of the National Academy of Sciences.

Fluorescent labels have long been useful to biomedical researchers interested in studying the structure and function of proteins and how they interact with their environment. Researchers “label” proteins by attaching a fluorophore, or fluorescent molecule, to the protein that they are interested in studying. In the past, the most commonly used fluorescent label was Green Fluorescent Protein (GFP), which comes from jellyfish.

However, since GFP is itself a protein, there are certain limitations to its use. For example, it can only be attached to the beginning or the end of the protein under investigation. Additionally, the size of this fluorescent label might alter the structure or function of the protein being studied, which has implications for the accuracy of the research.

To address this problem, the research team altered the genetic code of yeast, an easily manipulated eukaryotic organism, to incorporate an unnatural amino acid in addition to the common 20 amino acids. This new amino acid is fluorescent and has been synthesized chemically. It is approximately 200 times smaller than GFP and can be placed at specific sites within the protein being studied. Moreover, this technology enables the fluorescently labeled protein to be usable in both in vitro and in vivo – or both inside and outside of a living organism.

“The technique we devised for incorporating this fluorophore will allow researchers a much more efficient way to study the functions of proteins within living cells,” Deiters says. “Scientists will have much more control over the location of the fluorescent label within the protein, lending a higher degree of precision to their research.”

- peake -

Note to Editors: An abstract of the paper follows.

“A Genetically Encoded Fluorescent Amino Acid”

Authors:  Daniel Summerer, Scripps Research Institute; Alexander Deiters, North Carolina State University; et al
Published: June 19, 2006, online in Proceedings of the National Academy of Sciences

Abstract: The ability to introduce fluorophores selectively into proteins provides a powerful tool to study protein structure, dynamics, localization, and biomolecular interactions both in vitro and in vivo. Here, we report a strategy for the selective and efficient biosynthetic incorporation of a low-molecular-weight fluorophore into proteins at defined sites. The fluorescent amino acid 2-amino-3-(5-(dimethylamino)naphthatene-1-ulfonamido)proponate acid (dansylalanine) was genetically encoded in Saccharomyces cerevisiae by using an amber nonsense codon and corresponding orthogonal tRNA_aminoacyl-tRNA synthetase pair. This environmentally sensitive fluorophore was selectively introduced into human superoxide dismutase and used to monitor unfolding of the protein in the presence of guanidinium chloride. The strategy described here should be applicable to a number of different fluorophores in both prokaryotic and eukaryotic organisms, and it should facilitate both biochemical and cellular studies of protein structure and function.

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