Equilibrium and Kinetic Stability of a Hyperthermophilic Protein, O6-Methylguanine-DNA Methyltransferase under Various Extreme Conditions
| Autor: | Masahiro Okanojo, Kentaro Shiraki, Masahiro Takagi, Shingo Nishikori, Tadayuki Imanaka |
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| Rok vydání: | 2004 |
| Předmět: |
Protein Denaturation
Protein Folding Circular dichroism Hot Temperature Time Factors Protein Conformation hyperthermophilic protein Detergents Kinetics Biochemistry 2-Propanol O(6)-Methylguanine-DNA Methyltransferase chemistry.chemical_compound Protein structure Sodium dodecyl sulfate Guanidine Molecular Biology Ions Dose-Response Relationship Drug equilibrium stability Circular Dichroism Methanol protein unfolding Temperature kinetic stability Sodium Dodecyl Sulfate Trifluoroethanol General Medicine Thermococcus Crystallography chemistry Alcohols Thermodynamics Protein folding Mesophile |
| Zdroj: | Journal of Biochemistry. 136:503-508 |
| ISSN: | 0021-924X |
| DOI: | 10.1093/jb/mvh149 |
| Popis: | In this work we have studied the equilibrium and kinetic stability of a hyperthermophilic protein, O(6)-methylguanine-DNA methyltransferase (Tk-MGMT), and its mesophilic counterpart AdaC, in various chemical solutions. In an unfolding experiment using guanidine hydrochloride (GdnHCl), the unfolding free-energy change of Tk-MGMT at 30 degrees C was 42.0 kJ mol(-1), and the half time for unfolding was 4.5 x 10(6) s, which is much slower than that of AdaC and representative mesophilic proteins. In unfolding experiments using methanol, ethanol, 2-propanol, trifluoroethanol (TFE), and sodium dodecyl sulfate (SDS), Tk-MGMT retained its native structure at high concentrations, despite the fact that these chemical solutions affect protein conformations in a number of different ways. Kinetic studies using TFE and SDS indicate that the unfolding rates of Tk-MGMT in these solutions are slow as in GdnHCl. Further, the results of a mutational experiment suggest that an ion-pair network plays a key role in this slow unfolding. This slow rate of unfolding under extreme conditions is a significant property that distinguishes Tk-MGMT from mesophilic proteins. |
| Databáze: | OpenAIRE |
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