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D W Frederiksen

Publications and source records attributed to D W Frederiksen.

13 recordsLinked to original sources
PubMed1981

Hybrid myosins.

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Animals↗
PubMed1981

Calcium regulation of porcine aortic myosin.

Calcium regulation of actin-activated porcine aortic myosin MgATPase was studied. The MgATPase of the purified actomyosin was stimulated about 10-fold by 0.1 mM Ca2+. The 20,000 molecular weight light chain subunit (LC20) of myosin was phosphorylated by an endogenous kinase that required Ca2+. Half-maximal activation of both kinase and ATPase occurred at about 0.9 microM Ca2+. Phosphorylated and unphosphorylated myosins, free of actin, kinase, and phosphatase, were purified by gel filtration. The MgATPase of phosphorylated myosin was activated by rabbit skeletal muscle actin; unphosphorylated myosin was actin activated to a much lesser extent. Actin activation was maximal in the presence of Ca2+. Regulation of the aortic myosin MgATPase seems to involve both direct interaction of calcium with phosphorylated myosin and calcium activation of the myosin kinase. The MgATPase of trypsin-treated actomyosin did not require Ca2+ for full activity. The trypsin-treated actomyosin was devoid of LC20. When purified unphosphorylated aortic myosin was treated with trypsin, the LC20, was cleaved and the MgATPase, which was not appreciably actin activated before exposure to protease, was increased and was activated by skeletal muscle actin. After incubation of this light chain-depleted myosin with light chain from rabbit skeletal muscle myosin, the actin activation but not the increased activity, was abolished. Unphosphorylated LC20 seems to inhibit actin activation in this smooth muscle.

Actomyosin↗
PubMed1980

Physical and enzymatic properties of myosin from porcine brain.

Porcine brain myosin is a cytoplasmic protein similar to, but distinct from, its muscle counterpart. It has a high K+-ATPase activity at high ionic strength in EDTA and a low Mg+2-ATPase activity that is activated fivefold by either porcine brain or rabbit skeletal muscle actin. The molecule consists of three classes of subunits, with molecular weights of approximately 195,000 , 19,000, and 16,000. Brain myosin contains less glutamic acid, less lysine, and more threonine, serine, proline, and tyrosine than skeletal muscle myosin. The brain myosin extinction coefficient at 278 nm is 0.810 cm2/mg. Hydrodynamic studies yield an S020,w of 4.95S, a D020,w of 1.07 x 10(-7) cm2/s for brain myosin, and indicate that the molecules aggregate at high ionic strength. The molecular weight of the molecule, as calculated from extrapolation of D020,w/S20,w to zero concentration, is 444,000. The intrinsic viscosity of brain myosin is 0.191 ml/mg. These data are consistent with a highly asymmetric molecular species. Circular dichroism spectroscopy indicates that brain myosin is 58-60% alpha-helical in the presence of Ca+2 ions, and that removal of Ca+2 causes a small change in the spectrum.

Actins↗
PubMed1979

Physical properties of myosin from aortic smooth muscle.

Porcine aortic myosin is a smooth muscle contractile protein similar to its striated muscle counterpart. Electrophoresis in sodium dodecyl sulfate indicates that the molecule consists of three classes of subunits with polypeptide chain molecular weights of 192,000, 19,000, and 15,000. At 277 nm the absorption spectrum gives an extinction coefficient for aortic myosin of 0.558 cm2/mg; the circular dichroism spectrum of the protein indicates that aortic myosin contains about 70% of its residues in the alpha-helical configuration. Amino acid analysis shows that the smooth muscle myosin has significantly more arginine and leucine and significantly less valine and isoleucine than rabbit skeletal muscle myosin. Other studies yielded these data: Vapp = 0.716 mL/g [eta] = 0.213 mL/mg, S20, w = 5.84 x 10(-13)S. Similar studies with rabbit skeletal muscle myosin indicate that Vapp = 0.711 mL/g and S20, w = 6.36 x 10(-13)S. These properties suggest that aortic myosin, like skeletal muscle myosin, behaves hydrodynamically like a rigid rod.

Adenosine Triphosphatases↗
PubMed1976

Myosin-mediated Ca++-regulation of actomyosin-adenosinetriphosphatase from porcine aorta.

The nature of the Ca++-sensitive regulatory system for contraction of vascular smooth muscle is considered in detail. Smooth muscle actomyosin prepared from the medial layer of porcine aorta is analyzed chemically and its ATPase (adenosinetriphosphatase, EC 3.6.1.14) activities are investigated. The Mg++-ATPase of this vascular actomyosin is sensitive to the concentration of calcium in the range from 0.1 mM to 10 nM. The calcium sensitivity is maintained in the presence of excess pure actin from skeletal muscle and is abolished in the presence of pure skeletal myosin. It is concluded that the regulatory properties of this natural actomyosin from smooth muscle are in the myosin portion of the protein complex and are not bound to actin-tropomyosin as in skeletal muscle.

Actomyosin↗