Extrinsic protein stabilization by the naturally occurring osmolytes beta-hydroxyectoine and betaine.
Thermodynamic aspects of protein stabilization by two widespread naturally occurring osmolytes, beta-hydroxyectoine and betaine, were studied using differential scanning calorimetry (DSC) and bovine ribonuclease A (RNase A) as a model protein. The osmolyte beta-hydroxyectoine purified from Marinococcus was found to be a very efficient stabilizer. At a concentration of 3M it increased the melting temperature of RNase A (Tm) by more than 12K and gave rise to a stability increase of 10.6kJ/mol at room temperature. The heat capacity difference between the folded and unfolded state (deltaC(p)) was found to be significantly increased. Betaine stabilized RNase A only at concentrations less than 3M. Also, here deltaCp was found to be increased. Calculation of the number of water molecules that additionally bind to unfolded RNase A resulted in surprisingly low numbers for both osmolytes. The significant stabilization of RNase A by beta-hydroxyectoine makes this osmolyte an interesting stabilizer in biotechnological processes in which enzymes are applied in the presence of denaturants or at high temperature.
Knapp
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S
Karolinska Institute, Department of Biosciences at Novum, Center for Structural Biochemistry (CSB), Huddinge, Sweden. Stefan.Knapp@eu.pnu.com
Ladenstein
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R
Galinski
E A
EA
D000599:Amino Acids, Diamino / Q000737:chemistry*; D000818:Animals; D001622:Betaine / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D006094:Gram-Positive Bacteria / Q000737:chemistry*; D011489:Protein Denaturation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D013816:Thermodynamics
D000599:Amino Acids, Diamino; C121557:hydroxyectoine; D001622:Betaine; D012259:Ribonuclease, Pancreatic