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Results for “Ventricular Myosins”

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At least 19 recordsLinked to original sources
PubMed1979

Cardiac atrial myosin adenosine triphosphatase of animals and humans: distinctive enzymatic properties compared with cardiac ventricular myosin.

Cardiac myosin obtained from atria had a higher Ca2+-activated ATPase activity than did cardiac myosin from ventricles in various species of animals and in humans. The increased specific activity of Ca2+-activated adenosine triphosphatase (ATPase) of atrial myosin appeared to correlate with the level of the activity of ventricular myosin ATPase in the animal, since the same order in ATPase activity, as observed in ventricular myosins from various animals, was noted in atrial myosins. The enzymatic properties of atrial myosin also were characterized by no activation by N-ethylmaleimide, low activating energy, and a lower rate of inactivation at alkaline pH compared with the same properties of ventricular myosin. These findings suggest a difference in the myosin molecule at or near the active site, involving some sulfhydryl groups, between the two types of cardiac myosin. The Mg2+-activated ATPase activity, both in the presence and absence of actin (which is thought to be closely related to the basic contraction mechanism), also was enhanced in atrial myosin. Thus, the ATPase activities of atrial and ventricular myosins were different with special reference to the reaction pathway involving calcium and magnesium ions and appear to account for the difference in the velocity of contraction between the atria and the ventricles.

Adenosine Triphosphatases↗
PubMed1979

Comparative analysis of chicken atrial and ventricular myosins.

1. Structural and enzymic properties of myosins from atrial and ventricular cardiac muscle of the chicken were investigated and compared with myosins from the fast skeletal pectoralis and the slow skeletal anterior latissimus dorsi muscle. 2. The Ca2+-ATPase activity, both in function of pH and [K+], of atrial myosin closely resembled that of the fast pectoralis myosin, whereas the enzymic properties of ventricular myosin were similar to those of slow skeletal myosin. 3. By sodium dodecyl sulphate polyacrylamide gel electrophoresis on gradient gel and two-dimensional electrophoresis, involving isoelectric focusing in the first dimension and SDS gel electrophoresis in the second dimension, no difference could be demonstrated in the light-chain pattern of atrial and ventricular myosin. Complete identity was also found between anterior latissimus dorsi and cardiac light chains. 4. Electrophoretic analysis of soluble peptides released by tryptic digestion of myosin and electron microscopic study of light meromyosin paracrystals showed significant differences between the heavy chains of atrial and ventricular myosins, as well as between the heavy chains of cardiac and skeletal myosins. 5. The results confirm previous immunochemical findings and provide direct biochemical evidence for the existence of a new, unique type of myosin in the chicken atrial tissue.

Animals↗
PubMedDate not supplied

Binding of divalent cations by canine cardiac myosin: differences in normal right and left ventricles dependent upon number of light chains.

The moles of calcium bound by the left ventricle were 1.5 +/- 0.1, while those of the right ventricle were 2.9 +/- 0.2. The calcium binding constants were the same between myosins of the two cardiac ventricles. The Ca2+ binding constants were approximately 1.1 X 10(5) M-1 for both left and right ventricular myosins. Left ventricular myosin bound 1.3 +/- 0.1 mol of Mn2+, whereas right ventricular myosin bound 2.8 +/- 0.1 mol of Mn2+. The divalent cation Mn2+ only partially competed out Ca2+ (50%). Because of the partial competition, it seemed that Ca2+ and Mn2+ had some sights in common. These studies demonstrate a twofold difference in divalent cation binding (Ca2+, Mn2+) between left and right ventricular myosins. This variation in cation binding between the two ventricles is reflected in similar differences in myosin ATPase activity between the two ventricles.

Adenosine Triphosphatases↗
PubMed1975

Comparative analyses of skeletal and cardiac myosins.

Two types of canine cardiac myosins, from the free wall of the left ventricle and from the free wall of the right ventricle, were compared with canine skeletal muscle myosin from gastrocnemius. For K+ -activated myosin the Vmax values in mumoles of Pi/mg.min were: right ventricle, 0.57 +/- 0.02; left ventricle, 0.72 +/- 0.09; gastrocnemius, 0.92 +/- 0.04. For Ca++ -activated myosin the Vmax values were: right ventricle, 0.32 +/- 0.04; left ventricle, 0.42 +/- 0.03; gastrocnemius, 0.52 +/- 0.02; (p greater than 0.01 for all defferences). For all three types of tissues the Vmax values for NH4+ -activated myosin were the same (2.30 +/- 0.11). Corresponding to kinetic changes there were significant changes in the proportion and type of myosin subunits. In the two cardiac ventricles where heavy chains were immunologically identical, 81% of the total nitrogen of right ventricular myosin was present in the heavy chains whereas in left ventricular myosin 90% of the total nitrogen of myosin was present in the heavy chains. Quantifications were made on polyacrylamide gels were dye binding was directly related to nitrogen concentration for each of the myosin chains. In canine skeletal muscle gastrocnemius where the myosin heavy chains were immunologically nonidentical with those of cardiac myosin, 87% of the total nitrogen was present in the heavy chains. The data suggest that there are 2 moles of myosin light chains per mole of myosin heavy chains in right ventricular myosin where the adenosine triphosphatase (ATPase) activity is low and 1 mole of myosin light chains per mole of myosin heavy chains in left ventricula myosin where ATPase activity is elevated; for skeletal muscle myosin there were 1.5 moles of myosin light chains per mole of myosin heavy chains. Proportion of myosin light chain C1 to light chain C2 was the same in both left and right ventricular myosin. In skeletal muscle myosin the proportion of light chain C1 to light chain C2 was significantly different from that of cardiac tissue. It appears that the proportion of myosin light chain C1 to light chain C2 is directly related to the type of myosin heavy chain present since the immunologically identical heavy chains of cardiac tissue were immunologically nonidentical with those of skeletal muscle myosin.

Adenosine Triphosphatases↗
PubMed1978

The relationship of mechanical Vmax to myosin ATPase activity in rabbit and marmot ventricular muscle.

Papillary muscle mechanics and ventricular myosin calcium-activated ATPase activity were measured in the same heart as a function of temperature (8--28 degrees) in rabbits and marmots, in order to examine further the hypothesis that the velocity of cardiac muscle shortening at zero load (Vmax) is correlated with myosin ATPase activity. There was a similar Q10 for Vmax in each muscle type, as measured with isotonic afterloaded quick-releases at 30--33% time-to-peak tension; the calcium activated ATPase of myosin in the two muscle types also was similar. The least squares linear regression of rabbit Vmax on calcium-activated myosin ATPase activity was the same as in the marmot, so all the data were pooled to yield a linear regression (Y = 0.47 +/- 3.82X) with a high correlation between the two variables [r = 0.95, P less than 0.01 (ANOV)]. Furthermore, the correlation proved to be predictive of cardiac Vmax and myosin ATPase activity levels in other experiments where these two measurements decreased below normal as a result of hypertrophic growth. Consequently, the quantitative relationship between Vmax and myosin ATPase defined here may prove to be predictive of the ability of cardiac muscle to release bond energy.

Animals↗
PubMed1978

Immunological, electrophoretic and kinetic properties of cardiac myosins from various species.

1. In a homologous radioimmunoassay for canine ventricular myosin light chains, the following percentages of cross-reactivities were obtained using the dog as a reference: human, 28%; sheep, 21%; cat, 8%; guinea-pig, 7%; rabbit, 5%; and rat, 4%. 2. In a homologous double diffusion immunoassay using specific gamma G to canine cardiac myosin heavy chains, dog cardiac myosin showed immunological identity with human and sheep cardiac myosin but partial identity with myosins of other species. 3. On a 5-20% polyacrylamide gradient, light chain C1 was electrophoretically distinct in some species; light chain C2 was electrophoretically identical in all species. 4. The K+-activated myosin ATPase of small animals was higher than that of larger animals at an alkaline pH; the same was true for Ca2+-activated myosin when assayed at pH 6.3.

Animals↗
PubMed1979

Myosin synthesis and enzymatic properties during thyroxine intoxication in rabbits.

Hyperthyroidism has been induced to rabbits by a daily subcutaneous injection of D-L thyroxine (0.3 mg/kg). The ventricular myosin Ca2+ ATPase was increased after one week and reached + 100 % after two weeks while the K+ EDTA ATPase remained normal. During the same period, the heart weight, and the myosin incorporation of 3H-lysine after a four hour period of labelling had increased in parallel. The enhancement of both the Ca2+ ATPase and the labelling of myosin correlate, which suggests the appearance of a new molecule during the course of intoxication. This biochemical abnormality was unchanged after treatment with propranolol.

Animals↗
PubMed1975

Modulation of myosin in right ventricular hypertrophy.

Mild pulmonic stenosis was performed in dogs to evaluate the effect of systolic pressures overloading on the activity and subunits of myosin in the early hypertrophied right ventricle. Three weeks following pulmonary constriction, six hypertrophied dogs were sacrificed and compared to six sham-operated dogs which served as controls. In the right ventricular free wall of hypertrophied right ventricles (HRV), the heart/body weight was 46% greater than that of normal right ventricles (NRV) (p less than 0.01). Myosin ATPase activity (Vmax values) in mumoles phosphate/mg/min, was elevated significantly in the stressed ventricle for both K+ and Ca++ activity in hypertrophied right ventricles. Associated with the increase in myosin activity, there was an increase in proportion of heavy to light chains in myosin from HRV. There were approximately 2 moles of myosin light chains per mole of myosin heavy chains in NRV and approximately 1 mole of myosin light chains per mole of myosin heavy chains in HRV. The proportion of light chain C1 to C2, did not change in myosin from NRV and HRV. Of the C1 light chains, according to two-dimensional gel electrophoresis, there was less C1d as compared to C1c in HRV as compared to NRV. Thus K+- and Ca++- activated myosin is elevated in early canine HRV by pressure overload. It is suggested taht the augmented myosin activity is due to a reduction of light chain inhibition of myosin ATPase activity, which appears to result from the slower turnover rate of myosin light chains relative to heavy chains. Furthermore, when myosin light chains are added to hypertrophied right ventricular myosin, the ATPase activity is lowered.

Adenosine Triphosphatases↗
PubMed1979

The structure, function, and turnover of cardiac myosin in normal and myopathic Syrian hamsters.

Cardiac myosin was examined during the four pathologic stages of cardiomyopathy in strain BIO 14.6 of Syrian hamsters. It was determined that the Ca2+- and K+-ethylenediaminetetraacetic acid (EDTA)-activated ATPase activities of ventricular myosin were significantly reduced during the final stage of the inherited disease. One- and 2-dimensional gel electrophoresis of myosin samples at all stages failed to yield any evidence for a change in the subunit structure of myosin based on light chain number, molecular weight, and per cent composition. The final stage of the disease was characterized by altered protein metabolism. The rates of synthesis and degradation were both altered in the diseased tissue, and a net loss of myosin resulting from a substantial increase in the rate of degradation.

Adenosine Triphosphatases↗
PubMed2025

High-Sensitivity Top-Down Proteomics Reveals Enhanced Maturation of Micropatterned Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are increasingly used for disease modeling, drug discovery, and precision medicine, yet their utility is often limited by their immature phenotype. One promising maturation strategy involves using micropatterned substrates that mimic native cardiomyocytes' organizational growth and stiffness. However, the maturity of this model has not fully been assessed, and there is currently no method to extract proteins from micropatterned hiPSC-CMs for top-down proteomic analysis. Herein, we present a high-sensitivity protein extraction protocol for top-down proteomic analysis of hiPSC-CMs. Through this method, we assessed the maturation of micropatterned hiPSC-CMs compared to traditional monoculture and coculture monolayers at the proteoform level. We found that micropatterned hiPSC-CMs display molecular signatures of cardiomyocyte maturation including increased expression of ventricular myosin light chain isoforms, reduced expression of the fetal troponin T isoform, and decreased phosphorylation of alpha-tropomyosin. This high-sensitivity approach enables robust top-down proteomics from limited, heterogeneous cell populations and identifies the micropattern hiPSC-CM as a more adult-like CM model, broadening the utility of structured culture systems for cardiac disease modeling and translational research. Source data for this manuscript are available via MassIVE repository at massive.ucsd.edu with identifier: MSV000097864.

Myocytes, Cardiac↗
PubMed1979

The calcium binding properties of phosphorylated and unphosphorylated cardiac and skeletal myosins.

Porcine left ventricular cardiac myosin and rabbit white skeletal myosin were phosphorylated by rabbit skeletal myosin light chain kinase and their Ca2+ binding properties were examined by equilibrium dialysis techniques. No significant effect of phosphorylation on the Ca2+ binding properties of these myosins was observed. Both types of striated muscle myosins bound approximately 2 mol of Ca2+/mol of myosin with similar affinities of 3 x 10(7) M-1. In the presence of 3 x 10(-4) M Mg2+ the myosins bound Ca2+ with a reduced affinity of 3 to 4 x 10(5) M-1. Assuming competition between Mg2+ and Ca2+ for the binding sites on myosin, the changes in Ca2+ binding can be accounted for by a Mg2+ affinity of 2.5 to 3.0 x 10(5) M-1.

Animals↗