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The structure of the left-handed antiparallel amylose double helix: Theoretical studies

✍ Scribed by Wolfgang Schulz; Heinz Sklenar; Winfried Hinrichs; Wolfram Saenger

Publisher
Wiley (John Wiley & Sons)
Year
1993
Tongue
English
Weight
864 KB
Volume
33
Category
Article
ISSN
0006-3525

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✦ Synopsis

we have calculated a theoretical counterpart of this idealized double helix by constraining the helical twist and rise to their experimental values ( -45' and 2.33 A, respectively). Applying the same constraints to the parallel-stranded duplex, this also leads to a low-energy structure with wide central cavity. It is considered as an alternative model to accommodate iodine as observed in the starch-iodine complex.

Release of the helical constraints leads to left-handed antiparallel-and parallel-stranded double helices, respectively, with narrow central cavities. Both structures have very similar helix parameters and correspond, in their main characteristics, to the experimentally derived parallel-stranded structure of amylose in starch ( 6 residues per turn and a pitch height of about 21 A). The intramolecular energy calculated for the optimized antiparallel-stranded amylose double helix is comparable to that of the parallel-stranded structure. This result raises the question why parallel-stranded amylose seems to be favored in nature. 0 1992 John Wiley & Sons, Inc.

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