Differential scanning calorimetry (DSC) and conventional and saturation transfer electron paramagnetic resonance spectroscopy were used to study the rotational dynamics and structural stability of myosin in different states of the actomyosin ATPase cycle. DSC measurements supported the view that addition of nucleotides produced conformational changes in the multisubunit structure of myosins. The enthalpy of the thermal unfolding depended on the nucleotides; the conversion from a strongly attached state of myosin to actin to a weakly binding state was accompanied by an increase of the transition temperature which is caused by a change of the affinity of nucleotide binding to myosin. Myosins isolated from bovine heart and skeletal muscle from rabbit were spin-labelled with isothiocyanate-based probe molecules at the reactive sulfhydryl sites (Cys-697 and Cys-707) of the motor domain. In the presence of nonhydrolysable ATP analogue (AMP.PNP) and MgADP plus orthovanadate, conformational changes in the structure of myosins were detected. In the muscle fibre system, significant differences in the orientational dependence of spin labels were detected upon addition to nucleotides which showed changes in the rotational dynamics of myosin.
|Number of pages||7|
|Journal||High Temperatures - High Pressures|
|Publication status||Published - dec. 1 1998|
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanics of Materials
- Physical and Theoretical Chemistry