In a feat rivaling Mother Nature, chemists at Yale have made a protein-like molecule out of non-natural building blocks, according to a report featured online in the Journal of the American Chemical Society.
Nature uses alpha-amino acid building blocks to assemble the proteins that make life as we know it possible. Chemists at Yale now report evidence that nature could have used a different building block -- beta-amino acids -- and have shown that peptides assembled from beta-amino acids can fold into structures much like natural protein.
"The x-ray structure featured in the report shows a molecule that shares many of the structural characteristics of natural proteins," says principal author Alanna Schepartz, the Milton Harris '29 Ph.D. Professor of Chemistry at Yale and a Howard Hughes Medical Institute investigator. "Related studies show that the physical properties of the molecule are also remarkably similar to natural proteins. In other words, the beta-peptide assembly looks and acts a lot like a real protein."
The ability to mimic natural proteins makes beta-peptides powerful new tools for basic research and drug discovery. Like a taped recording, their greatest value
may be in their difference from a live performance.
"Since beta-peptides are not processed in the cell like natural peptides or proteins, it may be possible in the future to design beta-peptides that perform better or in more locations than current protein drugs," says Schepartz. "They also may have unique properties as biomaterials."
Natural proteins are composed of linear chains of alpha-amino acids. Beta-peptides are composed of beta-amino acids, which have an extra carbon in their backbone. Like alpha-amino acids, beta-amino acids are generated under simulated pre-biotic conditions, are isolated from meteorites and are byproducts of metabolism. However, they are not genetically encoded like natural proteins, nor are they built into chains by cells.
Since the early 1990s, scientists have been able to assemble beta-peptides into isolated helices. Until now, however, creating a structure that mimics the larger size and complex folded architecture of a natural protein had been an elusive goal. Schepartz's team solved the dilemma by designing a molecule that could form a bundle using characteristics found in natural proteins -- a greasy interior that repels water and a water-friendly exterior. This paper, which provides the first high-resolution picture of such a structure, shows a bundle of eight beta-peptides.
-- By Janet Rettig Emanuel
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