Experimental Data Snapshot

  • Resolution: 0.99 Å
  • R-Value Free: 0.100 
  • R-Value Observed: 0.088 

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This is version 2.3 of the entry. See complete history


V-Amylose at atomic resolution: X-ray structure of a cycloamylose with 26 glucose residues (cyclomaltohexaicosaose).

Gessler, K.Uson, I.Takaha, T.Krauss, N.Smith, S.M.Okada, S.Sheldrick, G.M.Saenger, W.

(1999) Proc Natl Acad Sci U S A 96: 4246-4251

  • DOI: https://doi.org/10.1073/pnas.96.8.4246
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The amylose fraction of starch occurs in double-helical A- and B-amyloses and the single-helical V-amylose. The latter contains a channel-like central cavity that is able to include molecules, "iodine's blue" being the best-known representative. Molecular models of these amylose forms have been deduced by solid state 13C cross-polarization/magic angle spinning NMR and by x-ray fiber and electron diffraction combined with computer-aided modeling. They remain uncertain, however, as no structure at atomic resolution is available. We report here the crystal structure of a hydrated cycloamylose containing 26 glucose residues (cyclomaltohexaicosaose, CA26), which has been determined by real/reciprocal space recycling starting from randomly positioned atoms or from an oriented diglucose fragment. This structure provides conclusive evidence for the structure of V-amylose, as the macrocycle of CA26 is folded into two short left-handed V-amylose helices in antiparallel arrangement and related by twofold rotational pseudosymmetry. In the V-helices, all glucose residues are in syn orientation, forming systematic interglucose O(3)n...O(2)(n+l) and O(6)n...O(2)(n+6)/O(3)(n+6) hydrogen bonds; the central cavities of the V-helices are filled by disordered water molecules. The folding of the CA26 macrocycle is characterized by typical "band-flips" in which diametrically opposed glucose residues are in anti rather than in the common syn orientation, this conformation being stabilized by interglucose three-center hydrogen bonds with O(3)n as donor and O(5)(n+l), O(6)(n+l) as acceptors. The structure of CA26 permitted construction of an idealized V-amylose helix, and the band-flip motif explains why V-amylose crystallizes readily and may be packed tightly in seeds.

  • Organizational Affiliation

    Institut für Kristallographie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany.



Entity ID: 1
MoleculeChains Length2D Diagram Glycosylation3D Interactions
A, B
Glycosylation Resources
GlyTouCan:  G58315AP
GlyCosmos:  G58315AP
Experimental Data & Validation

Experimental Data

  • Resolution: 0.99 Å
  • R-Value Free: 0.100 
  • R-Value Observed: 0.088 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 21.84α = 87.36
b = 22.92β = 89.51
c = 29.05γ = 61.98
Software Package:
Software NamePurpose
MAR345data collection
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1999-11-10
    Type: Initial release
  • Version 1.1: 2008-05-05
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Atomic model, Version format compliance
  • Version 1.3: 2012-09-05
    Changes: Derived calculations
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Database references, Derived calculations, Refinement description, Structure summary
  • Version 2.1: 2023-12-27
    Changes: Data collection, Database references, Structure summary
  • Version 2.2: 2024-03-13
    Changes: Source and taxonomy, Structure summary
  • Version 2.3: 2024-04-03
    Changes: Refinement description