Changes in rabbit skeletal myosin and its subfragments under high hydrostatic pressure

The pressure-induced denaturation of rabbit skeletal myosin and its subfragments under hydrostatic pressure were investigated. Four nanometer of red shift of the intrinsic fluorescence spectrum was observed in myosin under a pressure of 400 MPa. The ANS fluorescence of myosin increased with elevating pressure. Changes in the intrinsic fluorescence spectra of myosin and its subfragments were quantified and expressed as the center of spectral mass. The center of spectral mass of myosin and its subfragments linearly decreased with elevating pressure, and increased with lowering pressure. The fluorescence intensity of the ANS-labeled rod did not change during pressure treatment. The present results indicate that the most pressure-sensitive portion of myosin molecule is the head. Hysteresis of the center of spectral mass of S1 appeared under pressures above 300 MPa. Changes in the center of spectral mass of S1 above 350 MPa showed stronger hysteresis. The center of spectral mass did not decrease above 350 MPa during the compression process, indicating that S1 was stable in a partially denatured state at 350 MPa under pressure. The changes in the relative intensities of ANS fluorescence of S1 were measured under pressures up to 400 MPa, and the ANS fluorescence intensity increased with elevating pressure but it did not change after pressure release. The ANS fluorescence intensity increased under constant pressure suggesting that the pressure-induced denaturation of myosin was accelerated during pressurization.