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Protein Science, Vol 6, Issue 3 649-656, Copyright © 1997 by Cold Spring Harbor Laboratory Press
ARTICLE |
A. A. VAN-DIJK, E. DE-BOEF, A. BEKKERS, L. L. VAN-WIJK, E. VAN-SWIETEN, R. J. HAMER and G. T. ROBILLARD
Department of Biochemistry and Biophysical Chemistry and the Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands Present address: Gist Brocades N.V. Postbus 1, 2600 MA Delft, The Netherlands.
The structure of the central repetitive domain of high molecular weight (HMW) wheat gluten proteins was characterized in solution and in the dry state using HMW proteins Bx6 and Bx7 and a subcloned, bacterially expressed part of the repetitive domain of HMW Dx5. Model studies of the HMW consensus peptides PGQGQQ and GYYPTSPQQ formed the basis for the data analysis (van Dijk AA et al., 1997, Protein Sci 6:637-648). In solution, the repetitive domain contained a continuous nonoverlapping series of both type I and type II {beta}-turns at positions predicted from the model studies; type II {beta}-turns occurred at QPGQ and QQGY sequences and type I {beta}-turns at YPTS and SPQQ. The subcloned part of the HMW Dx5 repetitive domain sometimes migrated as two bands on SDS-PAGE; we present evidence that this may be caused by a single amino acid insertion that disturbs the regular structure of {beta}-turns. The type I {beta}-turns are lost when the protein is dried on a solid surface, probably by conversion to type II {beta}-turns. The homogeneous type II {beta}-turn distribution is compatible with the formation of a {beta}-spiral structure, which provides the protein with elastic properties. The {beta}-turns and thus the {beta}-spiral are stabilized by hydrogen bonds within and between turns. Reformation of this hydrogen bonding network after, e.g., mechanical disruption may be important for the elastic properties of gluten proteins.
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