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Published on June 30, 2006; 10.1104/pp.106.081935

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Received April 11, 2006
Accepted June 23, 2006

Cold Active Winter Rye Glucanases with Ice-Binding Capacity

Mahmoud W.F. Yaish *, Andrew C. Doxey , Brendan J. McConkey , Barbara A. Moffatt , and Marilyn Griffith

Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

* Corresponding author; email: myaish{at}uoguelph.ca.

Extracellular pathogenesis-related proteins including glucanases are expressed at cold temperatures in winter rye (Secale cereale L.) and display antifreeze activity. We have characterized recombinant cold-induced glucanases from winter rye in order to further examine their roles and contributions to cold-tolerance. Both basic {beta}-1,3-glucanases and an acidic {beta}-1,3;1,4-glucanase were expressed in Escherichia coli, purified, and assayed for their hydrolytic and antifreeze activities in vitro. All were found to be cold active and to retain partial hydrolytic activity at subzero temperatures (e.g. 14%-35% at -4°C). The two types of glucanases had antifreeze activity as measured by their ability to modify the growth of ice crystals. Structural models for the winter rye {beta}-1,3-glucanases were developed, on which putative ice-binding surfaces (IBSs) were identified. Residues on the putative IBS were charge conserved for each of the expressed glucanases, with the exception of one {beta}-1,3-glucanase recovered from non-acclimated (NA) winter rye in which a charged amino acid was present on the putative IBS. This protein also had a reduced antifreeze activity relative to the other expressed glucanases. These results support the hypothesis that winter rye glucanases have evolved to inhibit the formation of large, potentially fatal ice-crystals, in addition to having enzymatic activity with a potential role in resisting infection by psychrophilic pathogens. Glucanases of winter rye provide an interesting example of protein evolution and adaptation aimed to combat cold and freezing conditions.




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 Mol Biol EvolHome page
A. C. Doxey, M. W. F. Yaish, B. A. Moffatt, M. Griffith, and B. J. McConkey
Functional Divergence in the Arabidopsis {beta}-1,3-Glucanase Gene Family Inferred by Phylogenetic Reconstruction of Expression States
Mol. Biol. Evol., April 1, 2007; 24(4): 1045 - 1055.
[Abstract] [Full Text] [PDF]


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