Bending of smooth muscle myosin rod.
Electron microscopy of mammalian smooth muscle myosin rods showed them to be 153 +/- 7 nm (SD) long, and to bend sharply (greater than 90 degrees) but infrequently, and pH independently (range 6.5-9.5), at a single site 45 +/- 4 nm from one end of the molecule. Light meromyosin (LMM) preparations were 99 +/- 10 nm long, and showed no bends. Intrinsic viscosity vs temperature plots for rods and LMM indicated that neither fragment changed in flexibility in the range 4-40 degrees C. Peptide mapping in the presence and absence of SDS established that the proteolytic susceptibility of the hinge at the N terminus of LMM reflects the presence of locally different structure, and not simply a clustering of susceptible residues. The isolated smooth muscle myosin rod thus contains only a single hinge, having significant stiffness, and lacks the second bend seen under certain conditions in the intact molecule.
D000818:Animals; D002918:Chymotrypsin; D008854:Microscopy, Electron; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000032:analysis*; D015879:Myosin Subfragments; D009218:Myosins; D010446:Peptide Fragments; D011487:Protein Conformation; D013270:Stomach / Q000032:analysis; D013552:Swine; D013696:Temperature; D014783:Viscosity
D015879:Myosin Subfragments; D010446:Peptide Fragments; D002918:Chymotrypsin; D009218:Myosins