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1c58
From Proteopedia
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'''CRYSTAL STRUCTURE OF CYCLOAMYLOSE 26''' | '''CRYSTAL STRUCTURE OF CYCLOAMYLOSE 26''' | ||
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==About this Structure== | ==About this Structure== | ||
| - | + | Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1C58 OCA]. | |
==Reference== | ==Reference== | ||
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 SM, Okada S, Sheldrick GM, Saenger W, Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4246-51. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10200247 10200247] | 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 SM, Okada S, Sheldrick GM, Saenger W, Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4246-51. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10200247 10200247] | ||
| - | [[Category: Protein complex]] | ||
[[Category: Gessler, K.]] | [[Category: Gessler, K.]] | ||
[[Category: Nimz, O.]] | [[Category: Nimz, O.]] | ||
[[Category: Saenger, W.]] | [[Category: Saenger, W.]] | ||
| - | [[Category: | + | [[Category: Cycloamylose]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:20:41 2008'' | |
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Revision as of 09:20, 2 May 2008
CRYSTAL STRUCTURE OF CYCLOAMYLOSE 26
Overview
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.
About this Structure
Full crystallographic information is available from OCA.
Reference
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 SM, Okada S, Sheldrick GM, Saenger W, Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4246-51. PMID:10200247 Page seeded by OCA on Fri May 2 12:20:41 2008
