Requirement of the two-headed structure for the phosphorylation dependent regulation of smooth muscle myosin.
It is known for smooth muscle myosin that while acto-HMM ATPase activity is regulated by phosphorylation, acto-S-1 ATPase activity is not regulated. To clarify the heavy chain structure required for the regulation, smooth muscle myosin containing 7 different lengths of the S-2 portion were expressed in Sf9 insect cells using Baculovirus expression system. Myosin containing longer than 991 residues of heavy chain formed a stable two-headed structure while myosin with shorter than 944 residues of heavy chain formed a single-headed structure, indicating that the residues Gln945-Asp991 are critical for the formation of the two-headed structure. The actin activated ATPase activity of myosin mutants having a two-headed structure was activated by phosphorylation while that of myosin mutants that failed to form the two-headed structure was completely independent of phosphorylation. These results suggest that the two-headed structure is critical for the phosphorylation-dependent regulation.
Matsu-ura
M
M
Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4970, USA.
Ikebe
M
M
D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D066298:In Vitro Techniques; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000201:enzymology*; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism*; D009218:Myosins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins; D017384:Sequence Deletion; D014422:Turkeys
D015879:Myosin Subfragments; D011994:Recombinant Proteins; D000205:Actomyosin; D009218:Myosins