Transition from Natively Unfolded to Folded State Induced by Desiccation in an Anhydrobiotic Nematode Protein

Goyal, Kshamata and Tisi, Laurence and Basran, Amrik and Browne, John and Burnell, Ann and Zurdo, Jesus and Tunnacliffe, Alan (2003) Transition from Natively Unfolded to Folded State Induced by Desiccation in an Anhydrobiotic Nematode Protein. The Journal of Biological Chemistry, 278 (15). pp. 12977-12984.

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Late embryogenesis abundant (LEA) proteins are associated with desiccation tolerance in resurrection plants and in plant seeds, and the recent discovery of a dehydration- induced Group 3 LEA-like gene in the nematode Aphelenchus avenae suggests a similar association in anhydrobiotic animals. Despite their importance, little is known about the structure of Group 3 LEA proteins, although computer modeling and secondary structure algorithms predict a largely -helical monomer that forms coiled coil oligomers. We have therefore investigated the structure of the nematode protein, AavLEA1, in the first such analysis of a well characterized Group 3 LEA-like protein. Immunoblotting and subunit cross-linking experiments demonstrate limited oligomerization of AavLEA1, but analytical ultracentrifugation and gel filtration show that the vast majority of the protein is monomeric. Moreover, CD, fluorescence emission, and Fourier transform-infrared spectroscopy indicate an unstructured conformation for the nematode protein. Therefore, in solution, no evidence was found to support structure predictions; instead, AavLEA1 seems to be natively unfolded with a high degree of hydration and low compactness. Such proteins can, however, be induced to fold into more rigid structures by partner molecules or by altered physiological conditions. Because AavLEA1 is associated with desiccation stress, its Fourier transform-infrared spectrum in the dehydrated state was examined. A dramatic but reversible increase in -helix and, possibly, coiled coil formation was observed on drying, indicating that computer predictions of secondary structure may be correct for the solid state. This unusual finding offers the possibility that structural shifts in Group 3 LEA proteins occur on dehydration, perhaps consistent with their role in anhydrobiosis.

Item Type: Article
Keywords: Transition; anhydrobiotic; nematode; protein;
Academic Unit: Faculty of Science and Engineering > Biology
Item ID: 172
Depositing User: Prof. Ann Burnell
Date Deposited: 06 Jan 2005
Journal or Publication Title: The Journal of Biological Chemistry
Publisher: The American Society for Biochemistry and Molecular Biology.
Refereed: Yes

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