Conformation, filament assembly, and activity of single-headed smooth muscle myosin

被引:13
作者
Konishi, K [1 ]
Katoh, T [1 ]
Morita, F [1 ]
Yazawa, M [1 ]
机构
[1] Hokkaido Univ, Grad Sch Sci, Div Chem, Kita Ku, Sapporo, Hokkaido 0600810, Japan
关键词
extended and folded conformations; filament assembly; phosphorylation-dependent regulation; single-headed myosin; smooth muscle;
D O I
10.1093/oxfordjournals.jbchem.a022075
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Single-headed myosin was prepared by digestion of porcine aorta smooth muscle myosin with Staphylococcus aureus V8 protease in the presence of actin. The single-headed myosin preparation contained intact light chains, a rod fragment of a heavy chain, and a heavy chain of which only a minor fraction contained a nick in the head segment. Below 0.2 M NaCl, the single-headed myosin showed a decrease in Ca2+-ATPase activity and an increase in the elution time on gel filtration HPLC in a phosphorylation-dependent manner, indicating a phosphorylation-dependent conformational transition between the extended and folded forms. These conformations were confirmed by electron microscopic observation of rotary-shadowed samples of single-headed myosin. However, the conformational transition of single-headed myosin occurred in a narrower range with lower salt concentrations than that of double-headed myosin. The filament assembly of single-headed myosin was thus facilitated and phosphorylation-independent. The single-headed myosin also showed high actin-activated ATPase activity independent of phosphorylation. These results indicate that the two-headed structure of smooth muscle myosin is not essential for the conformational transition, but is required for the phosphorylation-dependent regulation of enzymatic activity and filament assembly.
引用
收藏
页码:163 / 170
页数:8
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