title: An unusual intrinsically disordered protein from the model legume Lotus japonicus stabilizes proteins in vitro.
abstract: Intrinsic structural disorder is a prevalent feature of proteins with chaperone activity. Using a complementary set of techniques, we have structurally characterized LjIDP1 (intrinsically disordered protein 1) from the model legume Lotus japonicus, and our results provide the first structural characterization of a member of the Lea5 protein family (PF03242). Contrary to in silico predictions, we show that LjIDP1 is intrinsically disordered and probably exists as an ensemble of conformations with limited residual beta-sheet, turn/loop, and polyproline II secondary structure. Furthermore, we show that LjIDP1 has an inherent propensity to undergo a large conformational shift, adopting a largely alpha-helical structure when it is dehydrated and in the presence of different detergents and alcohols. This is consistent with an overrepresentation of order-promoting residues in LjIDP1 compared with the average of intrinsically disordered proteins. In line with functioning as a chaperone, we show that LjIDP1 effectively prevents inactivation of two model enzymes under conditions that promote protein misfolding and aggregation. The LjIdp1 gene is expressed in all L. japonicus tissues tested. A higher expression level was found in the root tip proximal zone, in roots inoculated with compatible endosymbiotic M. loti, and in functional nitrogen-fixing root nodules. We suggest that the ability of LjIDP1 to prevent protein misfolding and aggregation may play a significant role in tissues, such as symbiotic root nodules, which are characterized by high metabolic activity.
authors.affiliation: Department of Molecular Biology, University of Aarhus, 8000 Aarhus, Denmark.
authors.forename: Svend
authors.initials: S
authors.lastname: Haaning
authors.forename: Simona
authors.initials: S
authors.lastname: Radutoiu
authors.forename: Søren V
authors.initials: SV
authors.lastname: Hoffmann
authors.forename: Jens
authors.initials: J
authors.lastname: Dittmer
authors.forename: Lise
authors.initials: L
authors.lastname: Giehm
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
authors.forename: Jens
authors.initials: J
authors.lastname: Stougaard
mesh_terms: D005816:Genetic Complementation Test / Q000379:methods; D000070116:Lotus / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism*
chemical_list: D018832:Molecular Chaperones; D010940:Plant Proteins; C066246:late embryogenesis abundant protein, plant
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