Evidence for involvement of a 12-residue peptide segment of the heavy chain in the neck region of smooth muscle myosin in formation of the 10S conformation.
Two synthetic peptides having amino acid sequences of the heavy chain segments in the neck region of porcine aorta smooth muscle myosin were used to study the formation of the 10S folded conformation. These peptides, MHC821-835 and MHC835-846, correspond to residues 821-835 and 835-846, respectively, of the chicken gizzard myosin heavy chain. The effects of these peptides on the filament formation of porcine aorta smooth muscle myosin were examined. The filamentous myosin fraction increased on the addition of MHC835-846 at NaCl concentrations lower than 0.25 M for both dephosphorylated and phosphorylated myosin, while the filament formation of dephosphorylated myosin was unaffected by the addition of MHC821-835 up to 30 microM. The filaments formed in the presence of MHC835-846 were observed by electron microscopy to be morphologically indistinguishable from those formed in the absence of the peptide. Rotary shadowed images of dephosphorylated myosin monomers revealed mostly the 10S form in the absence of MHC835-846, while the 6S form was predominant in the presence of the peptide. The results indicate that MHC835-846 inhibits the formation of the 10S conformation. On cosedimentation assaying with myosin, rod and light meromyosin, MHC835-846 bound to each of them with a stoichiometry of nearly 1 mol/mol heavy chain. Altogether, these results suggest that the region in the myosin heavy chain corresponding to MHC835-846 may be involved in the binding site for the light meromyosin portion of myosin for formation of the 10S conformation.
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo.
T
T
Katoh
T
T
Kodama
A
A
Fukushima
M
M
Yazawa
F
F
Morita
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000737:chemistry*; D018995:Myosin Heavy Chains / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D013552:Swine
D010446:Peptide Fragments; D018995:Myosin Heavy Chains