Distinctive Solvation Patterns Make Renal Osmolytes Diverse

Abstract

The kidney uses mixtures of five osmolytes to counter the stress induced by high urea and NaCl concentrations. The individual roles of most of the osmolytes are unclear, and three of the five have not yet been thermodynamically characterized. Here, we report partial molar volumes and activity coefficients of glycerophosphocholine (GPC), taurine, and myo-inositol. We derive their solvation behavior from the experimental data using Kirkwood-Buff theory. We also provide their solubility data, including solubility data for scyllo-inositol. It turns out that renal osmolytes fall into three distinct classes with respect to their solvation. Trimethyl-amines (GPC and glycine-betaine) are characterized by strong hard-sphere-like self-exclusion; urea, taurine, and myo-inositol have a tendency toward self-association; sorbitol and most other nonrenal osmolytes have a relatively constant, intermediate solvation that has components of both exclusion and association. The data presented here show that renal osmolytes are quite diverse with respect to their solvation patterns, and they can be further differentiated based on observations from experiments examining their effect on macromolecules. It is expected, based on the available surface groups, that each renal osmolyte has distinct effects on various classes of biomolecules. This likely allows the kidney to use specific combinations of osmolytes independently to fine-tune the chemical activities of several types of molecules.

Dimethylglycine Provides Salt and Temperature Stress Protection to Bacillus subtilis

“…For instance, the effects of the compatible solutes glycine betaine and proline on the cytoplasmic amounts of water and of the potassium, glutamate, and trehalose contents of osmotically stressed E. coli cells on the water activity and osmotic pressure of the cytoplasm are large enough to make glycine betaine a significantly better osmoprotectant than proline (77). Furthermore, there are important differences between various types of compatible solutes with respect to their solvation and water-structuring properties (78) and their abilities to preserve the functionality of macromolecules (4). A sizeable number of glycine betaine-and prolinerelated compounds serve as effective osmotic stress protectants of B. subtilis (10,79).…”

Abiotic stress protection by ecologically abundant dimethylsulfoniopropionate and its natural and synthetic derivatives: insights fromBacillus subtilis

“…The growth-enhancing effects of compatible solutes for osmotically stressed bacterial cells probably stem from a combination of their beneficial influence on cellular hydration and turgor, on the ionic strength and solvent properties of the cytoplasm, on the preservation of the solubility of proteins and their functionality, and on the maintenance of the integrity of cell components and biosynthetic processes (Cayley et al, 1992;Bourot et al, 2000;Bremer and Krämer, 2000;Diamant et al, 2001;Ignatova and Gierasch, 2006;Street et al, 2010;Auton et al, 2011;Wood, 2011). The physico-chemical attributes of individual compatible solutes (Street et al, 2006;Auton et al, 2011;Diehl et al, 2013;Jackson-Atogi et al, 2013) are, however, also an important determinant for the efficiency and type by which they exert their protective function. For instance, the oxidation of ectoine to 5-hydroxyectoine (Bursy et al, 2007) results in a far better desiccation protection for molecules than that afforded by its precursor ectoine (Tanne et al, 2014), which itself is an excellent stress protectant against various types of challenges (Lippert and Galinski, 1992;Widderich et al, 2014).…”

Plant-derived compatible solutes proline betaine and betonicine confer enhanced osmotic and temperature stress tolerance to Bacillus subtilis

“…The molecular and biochemical underpinning(s) of this type of temperature stress protection are far from clear (for a discussion of this issue, see Hoffmann & Bremer, 2011), but studies with glycine betaine have shown that the intracellular concentrations required for B. subtilis to sustain growth at very high or very low temperatures (Hoffmann & Bremer, 2011;Holtmann & Bremer, 2004) are far lower than those needed to achieve osmostress protection at high salinity . Hence, it seems possible that the temperature stress protection afforded by L-proline betaine and betonicine is routed in the physicochemical properties of these molecules (Cayley et al, 1992;Jackson-Atogi et al, 2013;Street et al, 2006) and the ensuing chemical chaperone function of compatible solutes that preserves the functionality of macromolecules and biosynthetic processes (Bourot et al, 2000;Chattopadhyay et al, 2004;Diamant et al, 2001;Fisher, 2006;Ignatova & Gierasch, 2006;Jackson-Atogi et al, 2013;Manzanera et al, 2002). The chemical differences between L-proline betaine and betonicine appear to be rather minor (Fig.…”

“…Factors other than the actual intracellular concentrations of L-proline betaine and betonicine also need to be taken into account when assessing the data. The physico-chemical properties of these solutes, their influence on the functionality of macromolecules, the transcriptional machinery of the cell and the solvation status of the cytoplasm might be sufficiently dissimilar to cause different physiological effects with respect to cell growth under osmotically challenging conditions (Cayley et al, 1992;Jackson-Atogi et al, 2013;Street et al, 2006;Wood, 2011).…”