TY - JOUR T1 - Equilibrium and kinetic stability of a hyperthermophilic protein, O6-methylguanine-DNA methyltransferase under various extreme conditions. AU - Nishikori,Shingo, AU - Shiraki,Kentaro, AU - Okanojo,Masahiro, AU - Imanaka,Tadayuki, AU - Takagi,Masahiro, PY - 2004/12/31/pubmed PY - 2005/9/13/medline PY - 2004/12/31/entrez SP - 503 EP - 8 JF - Journal of biochemistry JO - J Biochem VL - 136 IS - 4 N2 - 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. SN - 0021-924X UR - https://www.unboundmedicine.com/medline/citation/15625320/Equilibrium_and_kinetic_stability_of_a_hyperthermophilic_protein_O6_methylguanine_DNA_methyltransferase_under_various_extreme_conditions_ L2 - https://joi.jlc.jst.go.jp/JST.Journalarchive/biochemistry1922/136.503?lang=en&from=PubMed DB - PRIME DP - Unbound Medicine ER -