Protein-Water and Protein-Buffer Interactions in the Aqueous Solution of an Intrinsically Unstructured Plant Dehydrin: NMR Intensity and DSC Aspects

Abstract

Proton NMR intensity and differential scanning calorimetry measurements were carried out on an intrinsically unstructured late embryogenesis abundant protein, ERD10, the globular BSA, and various buffer solutions to characterize water and ion binding of proteins by this novel combination of experimental approaches. By quantifying the number of hydration water molecules, the results demonstrate the interaction between the protein and NaCl and between buffer and NaCl on a microscopic level. The findings overall provide direct evidence that the intrinsically unstructured ERD10 not only has a high hydration capacity but can also bind a large amount of charged solute ions. In accord, the dehydration stress function of this protein probably results from its simultaneous action of retaining water in the drying cells and preventing an adverse increase in ionic strength, thus countering deleterious effects such as protein denaturation.

The K-Segment of Maize DHN1 Mediates Binding to Anionic Phospholipid Vesicles and Concomitant Structural Changes

“…DHNs bind to a range of metal ions with multiple tandem His residues (Svensson et al, 2000;Kruger et al, 2002) and can bind a large number of solute ions (Tompa et al, 2006). For example, the Citrus unshiu CuCOR19 DHN protein binds Cu 2+ ions and scavenges reactive oxygen species, presumably to protect membranes from oxidative damage caused by water deficit (Hara et al, 2003(Hara et al, , 2005.…”

“…On the basis of compositional and biophysical properties and their link to abiotic stresses, several functions of DHNs have been proposed, including ion sequestration (Roberts et al, 1993), water retention (McCubbin et al, 1985), and stabilization of membranes or proteins (Close, 1996(Close, , 1997. Observations from in vitro experiments include DHN binding to lipid vesicles (Koag et al, 2003;Kovacs et al, 2008) or metals (Svensson et al, 2000;Heyen et al, 2002;Kruger et al, 2002;Alsheikh et al, 2003;Hara et al, 2005), protection of membrane lipid against peroxidation (Hara et al, 2003), retention of hydration or ion sequestration (Bokor et al, 2005;Tompa et al, 2006), and chaperone activity against the heat-induced inactivation and aggregation of various proteins (Kovacs et al, 2008).…”

Multifarious Roles of Intrinsic Disorder in Proteins Illustrate Its Broad Impact on Plant Biology

“…The functions of LEA proteins have been characterized mainly by in vitro experiments. These include binding of metal ions (Heyen et al, 2002;Hara et al, 2005;Rahman et al, 2011b) or lipid vesicles (Koag et al, 2003;Kovacs et al, 2008;Rahman et al, 2010), hydration or ion sequestration (McCubbin et al, 1985;Tompa et al, 2006), and, remarkably, stabilization of proteins and membranes in adaptation to abiotic stress ( Figure 2A, I to III). The latter function includes protection of various proteins against heat-induced inactivation or aggregation under stress conditions (Haaning et al, 2008;Boucher et al, 2010) and protection of membranes against drying and chilling (Tolleter et al, 2007;Rahman et al, 2010;Tolleter et al, 2010).…”

The Importance of Size and Disorder in the Cryoprotective Effects of Dehydrins

“…One possible answer is that dehydrins are also able to protect against other stresses. The K-, S-, and Y-segments are conserved so that they may carry out their other functions, such as binding ions (Alsheikh et al, 2003;Tompa et al, 2006), nucleic acids (Hara et al, 2009), and membranes (Rahman et al, 2010;. …”

“…Dehydrins are thought to be involved in dehydration protection, since their transcription and translation are increased during dehydration, and a correlation exists between drought tolerance and the amount of dehydrin present. In vitro, dehydrins have been shown to protect enzymes from freeze-thaw damage (Lin and Thomashow, 1992;Kazuoka and Oeda, 1994;Momma et al, 2003;Goyal et al, 2005;Hughes and Graether, 2011) and heat denaturation (Kovacs et al, 2008), interact with and protect membranes from cold and dehydrative stresses (Rahman et al, 2010;, and bind water (Tompa et al, 2006), ions (Alsheikh et al, 2003), and nucleic acids (Hara et al, 2009). Dehydrins have also been suggested to prevent the growth of ice crystals by functioning in a manner similar to antifreeze proteins (AFPs; Wisniewski et al, 1999;Simpson et al, 2005).…”