MtPM25 is an atypical hydrophobic late embryogenesis-abundant protein that dissociates cold and desiccation-aggregated proteins.

Late embryogenesis-abundant (LEA) proteins are one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. Among them, MtPM25, a member of the group 5 is specifically associated with DT in Medicago truncatula seeds. Its function is unknown and its classification as a LEA protein remains elusive. Here, evidence is provided that MtPM25 is a hydrophobic, intrinsically disordered protein that shares the characteristics of canonical LEA proteins. Screening protective activities by testing various substrates against freezing, heating and drying indicates that MtPM25 is unable to protect membranes but able to prevent aggregation of proteins during stress. Prevention of aggregation was also found for the water soluble proteome of desiccation-sensitive radicles. This inhibition was significantly higher than that of MtEM6, one of the most hydrophilic LEA protein associated with DT. Moreover, when added after the stress treatment, MtPM25 is able to rapidly dissolve aggregates in a non-specific manner. Sorption isotherms show that when it is unstructured, MtPM25 absorbs up to threefold more water than MtEM6. MtPM25 is likely to act as a protective molecule during drying and plays an additional role as a repair mechanism compared with other LEA proteins.

[1]  D. Hincha,et al.  Functional Divergence of Former Alleles in an Ancient Asexual Invertebrate , 2007, Science.

[2]  A. Tunnacliffe,et al.  LEA proteins prevent protein aggregation due to water stress. , 2005, The Biochemical journal.

[3]  E. Golovina,et al.  Membrane stabilization in the dry state. , 1997 .

[4]  J. Buitink,et al.  Glass formation in plant anhydrobiotes: survival in the dry state. , 2004, Cryobiology.

[5]  P. Tompa,et al.  Chaperone Activity of ERD10 and ERD14, Two Disordered Stress-Related Plant Proteins1[OA] , 2008, Plant Physiology.

[6]  W. Marcotte,et al.  Seed dehydration and the establishment of desiccation tolerance during seed maturation is altered in the Arabidopsis thaliana mutant atem6-1. , 2008, Plant & cell physiology.

[7]  S. Hoffmann,et al.  An Unusual Intrinsically Disordered Protein from the Model Legume Lotus japonicus Stabilizes Proteins in Vitro* , 2008, Journal of Biological Chemistry.

[8]  T. Labuza,et al.  Moisture-induced aggregation of whey proteins in a protein/buffer model system. , 2008, Journal of agricultural and food chemistry.

[9]  C. Dobson,et al.  Inherent toxicity of aggregates implies a common mechanism for protein misfolding diseases , 2002, Nature.

[10]  Hélène Rogniaux,et al.  Comparative Analysis of the Heat Stable Proteome of Radicles of Medicago truncatula Seeds during Germination Identifies Late Embryogenesis Abundant Proteins Associated with Desiccation Tolerance1[W] , 2006, Plant Physiology.

[11]  D. Renard,et al.  Temperature affects the supramolecular structures resulting from alpha-lactalbumin-lysozyme interaction. , 2007, Biochemistry.

[12]  E. Golovina,et al.  Mechanisms of plant desiccation tolerance. , 2001, Trends in plant science.

[13]  Lee Whitmore,et al.  DICHROWEB, an online server for protein secondary structure analyses from circular dichroism spectroscopic data , 2004, Nucleic Acids Res..

[14]  D. Hincha,et al.  LEA (Late Embryogenesis Abundant) proteins and their encoding genes in Arabidopsis thaliana , 2008, BMC Genomics.

[15]  C. Cho,et al.  Role of hydration water in protein unfolding. , 1999, Biophysical journal.

[16]  M. Hara,et al.  Radical scavenging activity and oxidative modification of citrus dehydrin. , 2004, Plant physiology and biochemistry : PPB.

[17]  J. Cushman,et al.  Temperature-Induced Extended Helix/Random Coil Transitions in a Group 1 Late Embryogenesis-Abundant Protein from Soybean1 , 2002, Plant Physiology.

[18]  M. Wise,et al.  The continuing conundrum of the LEA proteins , 2007, Naturwissenschaften.

[19]  E. Dickinson,et al.  Depletion flocculation of caseinate-stabilised emulsions: what is the optimum size of the non-adsorbed protein nano-particles? , 2004 .

[20]  N. Le Meur,et al.  Transcriptome profiling uncovers metabolic and regulatory processes occurring during the transition from desiccation-sensitive to desiccation-tolerant stages in Medicago truncatula seeds. , 2006, The Plant journal : for cell and molecular biology.

[21]  M. Kinoshita,et al.  On the energetics of protein folding in aqueous solution , 2006 .

[22]  J. Buitink,et al.  Metabolic dysfunction and unabated respiration precede the loss of membrane integrity during dehydration of germinating radicles. , 2000, Plant physiology.

[23]  D. Rubinsztein,et al.  Hydrophilic protein associated with desiccation tolerance exhibits broad protein stabilization function , 2007, Proceedings of the National Academy of Sciences.

[24]  P. Goloubinoff,et al.  Review: mechanisms of disaggregation and refolding of stable protein aggregates by molecular chaperones. , 2001, Journal of structural biology.

[25]  R. W. Visschers,et al.  Net charge affects morphology and visual properties of ovalbumin aggregates. , 2008, Biomacromolecules.

[26]  P. Tompa,et al.  Protein-water and protein-buffer interactions in the aqueous solution of an intrinsically unstructured plant dehydrin: NMR intensity and DSC aspects. , 2006, Biophysical journal.

[27]  E. Dickinson.  Hydrocolloids at interfaces and the influence on the properties of dispersed systems , 2003 .

[28]  A. Covarrubias,et al.  The Enigmatic LEA Proteins and Other Hydrophilins1[W] , 2008, Plant Physiology.

[29]  M. Wise,et al.  POPP the question: what do LEA proteins do? , 2004, Trends in plant science.

[30]  C. Kay,et al.  Hydrodynamic and optical properties of the wheat germ Em protein , 1985 .

[31]  Kelly M. Hines,et al.  A predicted N-terminal helical domain of a Group 1 LEA protein is required for protection of enzyme activity from drying. , 2007, Plant physiology and biochemistry : PPB.

[32]  M. Jaquinod,et al.  Structure and Function of a Mitochondrial Late Embryogenesis Abundant Protein Are Revealed by Desiccation[W] , 2007, The Plant Cell Online.

[33]  P. Srere.  Citrate-condensing enzyme-oxalacetate binary complex. Studies on its physical and chemical properties. , 1966, The Journal of biological chemistry.

[34]  P. Tompa,et al.  NMR relaxation studies on the hydrate layer of intrinsically unstructured proteins. , 2005, Biophysical journal.

[35]  V. Lumbreras,et al.  Arabidopsis thaliana Atrab28: a nuclear targeted protein related to germination and toxic cation tolerance , 2002, Plant Molecular Biology.

[36]  P. Gustafsson,et al.  Structural Investigation of Disordered Stress Proteins. Comparison of Full-Length Dehydrins with Isolated Peptides of Their Conserved Segments1 , 2006, Plant Physiology.

[37]  Hui Wei,et al.  Functional dissection of hydrophilins during in vitro freeze protection. , 2008, Plant, cell & environment.

[38]  R. Hell,et al.  A Metal-binding Member of the Late Embryogenesis Abundant Protein Family Transports Iron in the Phloem ofRicinus communis L.* , 2002, The Journal of Biological Chemistry.