PRESSURE ENHANCES THERMAL-STABILITY OF DNA-POLYMERASE FROM 3 THERMOPHILIC ORGANISMS

DNA polymerases derived from three thermophilic microorganisms, Pyroco ccus strain ES4, Pyrococcus furiosus, and Thermus aquaticus, were stab ilized in vitro by hydrostatic pressure at denaturing temperatures of 111 degrees C, 107.5 degrees C, and 100 degrees C (respectively). Inac tivation rates, as determined by enzyme activity measurements, were me asured at 3, 45, and 89MPa. Half-lives of P. strain ES4, P. furiosus, and T. aquaticus DNA polymerases increased from 5.0, 6.9, and 5.2 minu tes (respectively) at 3 MPa to 12, 36, and 13 minutes (respectively) a t 45MPa. A pressure of 89MPa further increased the half-lives of P. st rain ES4 and T. aquaticus DNA polymerases to 26 and 39 minutes, while the half-life of P. furiosus DNA polymerase did not increase significa ntly from that at 45 MPa. The decay constant for P. strain ES4 and T. aquaticus polymerases decreased exponentially with increasing pressure , reflecting an observed change in volume for enzyme inactivation of 6 1 and 73 cm(3)/ mel, respectively. Stabilization by pressure may resul t from pressure effects on thermal unfolding or pressure retardation o f unimolecular inactivation of the unfolded state. Regardless of the m echanism, pressure stabilization of proteins could explain the previou sly observed extension of the maximum temperature for survival of P. s train ES4 and increase the survival of thermophiles in thermally varia ble deep-sea environments such as hydrothermal vents.