Conformational and rheological changes of high-pressure processing treated rabbit myosin subfragments during heating

Rabbit skeletal (M. psoas) myosin subunits, heavy meromyosin (HMM) and light meromyosin (LMM), were purified and treated by high pressure processing (HPP). The HPP (100, 200 and 300 MPa)-modified myosin subunits were subjected to thermal treatment (25-70 degrees C), during which their conformational and rheological properties were explored. The turbidity of all HMM and LMM samples slightly improved from 25 to 55 degrees C, and then sharply increased from 55 degrees C to 70 degrees C (from). Pressure >= 200 MPa changed the structural properties of HMM, exhibited as more exposed hydrophobic and sulfhydryl patches, whereas the increase of hydrophobicity induced by heating decelerated afterwards. The LMM portion exhibited inferior heating stability. Upon heating, both pressurized and nontreated HMM showed similar trends of changes of secondary structure, which included the reduction of a-helices and the increase of (1-structures. Only a slight change of secondary structure occurred on LMM after HPP, indicating a higher resistance of LMM on HPP than HMM. These findings suggested that a moderate denaturation generated by HPP would not affect the thermal behavior of myosin subfragments, while pressures of >= 200 MPa might lead to disadvantageous rheological properties by mediating the thermophysical properties of HMM.