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Myosin from arterial smooth muscle: isolation following actin depolymerization.
Metadata
JournalBiochim. Biophys. ActaNot FoundDate
1975-Dec-15
Publication Type
Research Support, U.S. Gov't, P.H.S.
Journal Article
Comparative Study
Volume
1975-Dec-15 / 412 : 241-55
Author
Megerman J , Murphy RA
DoiPMIDMESH
Actins
Actomyosin
Adenosine Triphosphatases
Adenosine Triphosphate
Animals
Carotid Arteries
Cats
Chemical Precipitation
Dialysis
Dogs
Hydrogen-Ion Concentration
Molecular Weight
Muscle, Smooth
Myosins
Osmolar Concentration
Polyethylene Glycols
Potassium Chloride
Solubility
Swine
Abstract
The contractile proteins from arterial smooth muscle are highly soluble, and can be extracted at I = 0.05. However, they can be precipitated by a prolonged dialysis at pH 6 to give an actomyosin with a high, although variable, actin:myosin ratio. The sedimentation behavior of this actomyosin at high ionic strength was examined as a function of pH, protein concentration and composition by preparative ultracentrifugation. Comparisons with synthetic skeletal muscle actomyosins of similar composition demonstrated significant differences in the behaviors of these two systems. It was found that much smooth muscle actomyosin is not dissociated by normally relaxing conditions, and that it sediments at a slower rate than F-actin. The solubility of the supernatant protein (a myosin-enriched actomyosin) in 0.2 M K Cl (pH 7) depended on the pH during centrifugation. A lower solubility was associated only with a higher actin concentration in the supernatant, suggesting a dependence on actin repolymerization. Pure myosin was selectively precipitated from the supernatant by polyethylene glycol-6000, but only when the protein was soluble at low ionic strength. The solubility of purified myosin was similar to that of myosin from striated muscles. A relationship between the presence of depolymerized actin and the high solubility of smooth muscle contractile proteins is suggested.
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