Glycine stops the end of a protein spiral, providing a 'helix cap', because it can adopt a left-handed conformation, reveals a paper in the March issue of Nature Chemical Biology. A major structural feature of proteins, spirals called alpha-helices, often end in the smallest amino acid, glycine. It was not known if glycine was preferred because it is the only amino acid that can adopt a left-handed conformation or because it lets more water through since it is the smallest amino acid.
Stephen Kent, George Makhatadze, and colleagues made proteins in which the end of an alpha-helix contained either a natural amino acid or a non-natural 'left-handed' amino acid. By comparing the stabilities of proteins with a natural or the corresponding left-handed amino acid at the end of a spiral, the authors found that adopting a left-handed conformation was critical for stopping further spiraling of the alpha-helix.
This increased understanding of protein structure could have important implications for designing new proteins with improved properties, perhaps using left-handed amino acids.
Stephen Kent (University of Chicago, Chicago, IL, USA)
George Makhatadze (Pennsylvania State University, Hershey, PA, USA)
Abstract available online.
(C) Nature Chemical Biology press release.
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