2fcq
From Proteopedia
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X-ray Crystal Structure of a Chemically Synthesized Ubiquitin with a Cubic Space Group
Overview
The alpha-helix is a fundamental protein structural motif and is, frequently terminated by a glycine residue. Explanations for the, predominance of glycine at the C-cap terminal portions of alpha-helices, have invoked uniquely favorable energetics of this residue in a, left-handed conformation or enhanced solvation of the peptide backbone, because of the absence of a side chain. Attempts to quantify the, contributions of these two effects have been made previously, but the, issue remains unresolved. Here we have used chemical protein synthesis to, dissect the energetic basis of alpha-helix termination by comparing a, series of ubiquitin variants containing an L-amino acid or the, corresponding D-amino acid at the C-cap Gly35 position. D-Amino acids can, adopt a left-handed conformation without energetic penalty, so the, contributions of conformational strain and backbone solvation can thus be, separated. Analysis of the thermodynamic data revealed that the preference, for glycine at the C' position of a helix is predominantly a, conformational effect.
About this Structure
2FCQ is a Single protein structure of sequence from [1] with CD as ligand. Full crystallographic information is available from OCA.
Reference
Dissecting the energetics of protein alpha-helix C-cap termination through chemical protein synthesis., Bang D, Gribenko AV, Tereshko V, Kossiakoff AA, Kent SB, Makhatadze GI, Nat Chem Biol. 2006 Mar;2(3):139-43. Epub 2006 Jan 30. PMID:16446709
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