Myosin Synthesis and Degradation during Development …

AB - Although insulin's anticatabolic effect on protein metabolism in type 1 diabetes has been clearly shown to be related to the inhibition of protein breakdown, insulin's effect on muscle protein synthesis remains controversial. Cross-limb studies and measurements of synthesis rates of mixed muscle protein have yielded conflicting results. These measurements represent the mean synthesis of several muscle proteins and may miss changes in the synthesis rates of individual muscle proteins. We measured the fractional synthesis rates of myosin heavy chain (MHC), the principal muscle contractile protein, and mixed muscle protein (MMP) in six type 1 diabetic patients during insulin deprivation and insulin treatment. Comparisons were made with six healthy control subjects. Muscle biopsies were taken at 2 h and 8 h during a primed continuous infusion of L-[1-13C]leucine. MHC was purified by a preparative continuous elution gel electrophoresis, and fractional synthesis rates were calculated. We found that in type 1 diabetic subjects, the fractional synthesis rates of MHC and MMP during insulin treatment are similar to those of control subjects. Acute insulin deprivation did not affect either the synthesis rate or the ratio of MHC to MMP in type 1 diabetic subjects. In the postabsorptive state, acute insulin deprivation has no effect on MHC or MMP synthesis in type 1 diabetic patients.

07/01/2018 · Myosin Synthesis and..

AB - Polyadenylylated RNA, extracted from differentiating primary cultures of rat muscle and the myogenic cell line L8, directs the synthesis of polypeptides in the wheat germ cell free system which comigrate with myosin light chains under several electrophoretic conditions. The peptides also associate specifically with heavy myosin subunits during dissociation reassociation treatment. Intact cells of primary skeletal muscle cultures and of the myogenic line synthesize predominantly two light chains. RNA extracted from primary muscle cultures directs the synthesis of a third polypeptide in the cell free system, similar to the third light chain found in myosin extracted from adult rat thigh muscle. Products of cell free systems directed by RNA extracted from fibroblasts, reticulocytes, and myeloma cells did not contain detectable amounts of similar polypeptides.


Synthesis of myosin heavy and light chains ..

These cells synthesized the 200,000-dalton heavy chain of myosin (MHC) at a rate of 3.2 x 10(3) molecules/cell/min.

RNA extracted from primary muscle cultures directs thesynthesis of a third polypeptide in the cell-free system, similar to thethird light chain found in myosin extracted from adult rat thigh muscle.


Amino Acid Derivatives: Catecholamine, …

The weight ratio of myosin/actin, the myosin heavy chain content as the percentage of total protein (wt/wt), and the kinds of myosin light chains were determined in (a) standard muscle cultures, (b) pure myotube cultures, and (c) fibroblast cultures. Cells for these cultures were obtained from the breast of 11-day chick embryos. Standard cultures contain, in addition to myotubes, large numbers of replicating mononucleated cells. By killing these replicating cells with cytosine arabinoside, pure myotube cultures were obtained. The myosin/actin ratio (wt/wt) for pure myotube, standard muscle, and fibroblast cultures average 3.1, 1.9, and 1.1 respectively. By day 7, myosin in myotube cultures represents a minimum of 7% of the total protein, but about 3% in standard cultures and less than 1.5% in fibroblasts cultures. Myosin from standard cultures contains light chain LC1, LC2, and LC3, with a relative stoichiometry of the molarity of 1.0:1.9:0.5 and mol wt of 25,000, 18,000 and 16,000 daltons, identical to those in adult fast muscle. Myosin from pure myotubes exhibits light chains LC1 and LC2, with a molar ratio of 1.5:1.6. Myosin from fibroblast cultures possesses two light chains with a stoichiometry of 1.8:1.8 and mol wt of 20,000 and 16,000 daltons. Clearly, the faster migrating light chain, LC3, found in standard cultures is synthesized not by the myotubes but ty the mononucleated cells. In myotubes, both the assembly of the sarcomeres and the interaction between thick and thin filaments required for spontaneous contraction occur in the absence of light chain LC3. One set of structural genes for the myosin light and heavy chains appears to be active in mononucleated cells, whereas another set appears to be active in multinucleated myotubes.

01/10/2015 · SpringerLink

Polyadenylylated RNA, extracted from differentiating primary cultures of rat muscle and the myogenic cell line L8, directs the synthesis of polypeptides in the wheat germ cell free system which comigrate with myosin light chains under several electrophoretic conditions. The peptides also associate specifically with heavy myosin subunits during dissociation reassociation treatment. Intact cells of primary skeletal muscle cultures and of the myogenic line synthesize predominantly two light chains. RNA extracted from primary muscle cultures directs the synthesis of a third polypeptide in the cell free system, similar to the third light chain found in myosin extracted from adult rat thigh muscle. Products of cell free systems directed by RNA extracted from fibroblasts, reticulocytes, and myeloma cells did not contain detectable amounts of similar polypeptides.