2FCN: X-Ray Crystal Structure Of A Chemically Synthesized [d-Val35]ubiquitin With A Cubic Space Group

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.
PDB ID: 2FCNDownload
MMDB ID: 37341
PDB Deposition Date: 2005/12/12
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 2FCN: monomeric; determined by author
Molecular Components in 2FCN
Label Count Molecule
Protein (1 molecule)
Ubiquitin(Gene symbol: UBC)
Molecule annotation
Chemicals (9 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB