title: Effects of nucleotide on skeletal muscle myosin unfolding in myofibrils by DSC.
abstract: The thermal unfolding of myosin in skeletal muscle myofibrils was studied by differential scanning calorimetry (DSC). In the absence of nucleotide two major transitions with Tm of 52 degrees C and 58 degrees C, and a minor transition with Tm of 19 degrees C were detected. The unfolding can be characterized with a total enthalpy of -90 +/- 6.1 mJ/g protein. The major transition with Tm of 58 degrees C was independent of the presence of nucleotide and orthovanadate (Vi), and it can be assigned to the unfolding of the alpha-helical rod part of myosin and partly to actin. In the presence of MgADP, the minor transition shifted to higher temperature, indicating changes between the heavy chain of subfragment-1 and the LC-2 light chain. The transition with Tm of 52 degrees C exhibited a significant broadening and a small shift to lower temperature. It indicates an internal domain or segmental rearrangement of the myosin motor. Upon addition of MgADP and Vi, a shift to higher temperature was observed for the lower major transition, evidencing that with trapped ADP and Vi the intermolecular interactions stabilized the myosin head region.
authors.affiliation: Department of Biophysics, University Medical School, Pécs, Hungary.
authors.forename: D
authors.initials: D
authors.lastname: Lörinczy
authors.forename: J
authors.initials: J
authors.lastname: Belagyi
mesh_terms: D000205:Actomyosin / Q000737:chemistry*; D000244:Adenosine Diphosphate / Q000737:chemistry*; D000818:Animals; D002152:Calorimetry, Differential Scanning; D009119:Muscle Contraction; D009218:Myosins / Q000737:chemistry*; D011489:Protein Denaturation; D011817:Rabbits; D013816:Thermodynamics; D014638:Vanadates / Q000737:chemistry
chemical_list: D014638:Vanadates; D000244:Adenosine Diphosphate; D000205:Actomyosin; D009218:Myosins