scholarly journals The relaxing protein system of striated muscle. Resolution of the troponin complex into inhibitory and calcium ion-sensitizing factors and their relationship to tropomyosin

1969 ◽  
Vol 115 (5) ◽  
pp. 993-1004 ◽  
Author(s):  
M. C. Schaub ◽  
S V Perry
Keyword(s):  
Ionic Strength ◽  
Adenosine Triphosphatase ◽  
Striated Muscle ◽  
Inhibitory Effect ◽  
Inhibitory Factor ◽  
Adenosine Triphosphatase Activity ◽  
Protein System ◽  
Maximum Inhibition ◽  
Troponin Complex ◽  
Low Ionic Strength

1. A method involving isoelectric precipitation and chromatography on SE-Sephadex (sulphoethyl-Sephadex) is described for the preparation of the troponin complex free of tropomyosin from low-ionic-strength extracts of natural actomyosin and myofibrils. 2. Purified troponin complex required tropomyosin to inhibit the Mg2+-stimulated adenosine triphosphatase activity and superprecipitation of desensitized actomyosin in the presence of ethanedioxybis(ethylamine)tetra-acetate. An upper limit of 35000 for the ‘molecular weight’ of the troponin complex was derived from the amounts required to bring about 50% of the maximum inhibition of the Mg2+-stimulated adenosine triphosphatase activity of desensitized actomyosin of known concentration. 3. In the presence of dissociating reagents the troponin complex could be dissociated into inhibitory and Ca2+-sensitizing factors, which could be isolated separately on SE-Sephadex. The inhibitory factor inhibited the Mg2+-stimulated adenosine triphosphatase activity and superprecipitation of desensitized actomyosin independently of the concentration of free Ca2+ in the medium. 4. The Ca2+-sensitizing factor changed its electrophoretic mobility on polyacrylamide gel in the presence of ethanedioxybis(ethylamine)tetra-acetate. It formed a complex with the inhibitory factor at low ionic strength and the original biological activity of the troponin complex could be restored on mixing the inhibitory factor with the Ca2+-sensitizing factor in the ratio of about 3:2. 5. Evidence is presented indicating that the ability of tropomyosin preparations to restore relaxing-protein-system activity to the troponin complex and their inhibitory effect on the Ca2+-stimulated adenosine triphosphatase activity of desensitized actomyosin are two properties of different stability to preparative procedures and tryptic digestion. This suggests that the relaxing protein system of muscle may contain another as yet uncharacterized component.

scholarly journals Effect of bivalent cations on the adenosine triphosphatase of actomyosin and its modification by tropomyosin and troponin

1969 ◽  
Vol 111 (5) ◽  
pp. 777-783 ◽  
Author(s):  
M. C. Schaub ◽  
M. Ermini
Keyword(s):  
Ionic Strength ◽  
Metal Ions ◽  
Metal Ion ◽  
Adenosine Triphosphatase ◽  
Ionic Radius ◽  
Unique Feature ◽  
Optimum Concentration ◽  
Adenosine Triphosphatase Activity ◽  
Bivalent Cations ◽  
Low Ionic Strength

1. After removal of tropomyosin and troponin from the ‘natural’ actomyosin complex, the adenosine triphosphatase activity of the resulting ‘desensitized’ actomyosin is stimulated to the same extent by various bivalent cations with an ionic radius in the range 0·65–0·99å when tested at optimum concentration of the metal ion in the presence of 2·5mm-ATP at low ionic strength and pH7·6. Under identical conditions the adenosine triphosphatase activity of myosin alone is stimulated to an appreciable extent only by Ca2+ (ionic radius 0·99å). 2. Tropomyosin narrows the range of size of the stimulatory cations by inhibiting specifically the adenosine triphosphatase activity of ‘desensitized’ actomyosin when stimulated by Ca2+ or the slightly smaller Cd2+ (ionic radius 0·97å). Tropomyosin has no effect on the adenosine triphosphatase activity of ‘desensitized’ actomyosin when stimulated by the smaller cations, nor on the Ca2+-activated adenosine triphosphatase activity of myosin alone. 3. The adenosine triphosphatase activity of the ‘natural’ actomyosin system (containing tropomyosin and troponin) stimulated by the smallest cation, Mg2+ (ionic radius 0·65å), is low when the system is deprived of Ca2+ but high in the presence of small amounts of Ca2+. This sensitivity to Ca2+ seems to be a unique feature of the Mg2+-stimulated system. 4. The changes in specificity of the myosin adenosine triphosphatase activity in its requirement for bivalent cations caused by interaction with actin, tropomyosin and troponin primarily concern the size of the metal ions. The effects on enzymic properties of myofibrils due to tropomyosin and troponin can be demonstrated at low and at physiological ionic strength.

Filament Formation by Slime Mould Myosin Isolated at Low Ionic Strength

1974 ◽  
Vol 15 (1) ◽  
pp. 113-129
Author(s):  
H. HINSSEN ◽  
J. D'HAESE
Keyword(s):  
Ionic Strength ◽  
Striated Muscle ◽  
Divalent Cations ◽  
Filament Formation ◽  
Selective Precipitation ◽  
Slime Mould ◽  
Preparation Conditions ◽  
Filament Structure ◽  
Low Ionic Strength

Myosin was isolated and purified from plasmodia of the slime mould Physarum polycephalum by a new method. This method is based on actomyosin extraction at low ionic strength after extensive washing, followed by the selective precipitation of myosin at pH 6.1 under relaxing conditions. The yield of myosin was 3-5 times higher than reported for other methods. In contrast to earlier studies a remarkably strong tendency to filament formation was found for slime mould myosin, probably due to a better preservation of some structural properties during preparation. Conditions were worked out under which numerous filaments up to 4 µm in length can be produced. It was established that not only a gradual decrease of ionic strength may influence filament formation, but also pH, ATP concentration and the presence of divalent cations. Compared to the current filament models a difference exists in the structure of the filaments. No central bare zone can be found, and thus, they lack an apparent bipolarity. Along the entire filament there are lateral projections representing the head portion of myosin molecules. A clear periodicity with an axial repeat of about 14 nm was observed, indicating a highly ordered arrangement of these projections. In this paper it is shown for the first time that myosin from one of the primitive motile systems is able to form aggregates of high structural order, indicating that the contraction of non-muscular actomyosin systems is not necessarily effected with oligomeric or randomly aggregated myosin. The possible role of myosin aggregation in vivo and the similarity of filament structure to that recently reported for myosin from vertebrate smooth muscle and striated muscle are discussed.

scholarly journals Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

1972 ◽  
Vol 59 (4) ◽  
pp. 375-387 ◽  
Author(s):  
William Lehman ◽  
Andrew G. Szent-Györgyi
Keyword(s):  
Ionic Strength ◽  
Atpase Activity ◽  
Adenosine Triphosphatase ◽  
Limulus Polyphemus ◽  
Muscle Tropomyosin ◽  
Low Ionic Strength ◽  
Full Activation

Purified actin does not stimulate the adenosine triphosphatase (ATPase) activity of Limulus myosin greatly. The ATPase activity of such reconstituted preparations is only about one-fourth the ATPase of myofibrils or of natural actomyosin. Actin preparations containing tropomyosin, however, activate Limulus myosin fully. Both the tropomyosin and the actin preparations appear to be pure when tested by different techniques. Tropomyosin combines with actin but not with myosin and full activation is reached at a tropomyosin-to-actin ratio likely to be present in muscle. Tropomyosin and actin of several different animals stimulate the ATPase of Limulus myosin. Tropomyosin, however, is not required for the ATPases of scallop and rabbit myosin which are fully activated by pure actin alone. Evidence is presented that Limulus myosin, in the presence of ATP at low ionic strength, has a higher affinity for actin modified by tropomyosin than for pure actin.

scholarly journals The effect of tropomyosin on the adenosine triphosphatase activity of desensitized actomyosin

1967 ◽  
Vol 105 (3) ◽  
pp. 1235-1243 ◽  
Author(s):  
M. C. Schaub ◽  
S V Perry ◽  
D. J. Hartshorne
Keyword(s):  
Acetic Acid ◽  
Inhibitory Activity ◽  
Adenosine Triphosphatase ◽  
Inhibitory Effect ◽  
Tryptic Digestion ◽  
Prolonged Treatment ◽  
Thiol Groups ◽  
Protein Thiol ◽  
Adenosine Triphosphatase Activity ◽  
Inhibitory Activities

1. Tropomyosin preparations of the Bailey type, and those prepared in the presence of dithiothreitol to prevent oxidation of protein thiol groups, inhibit the Ca2+-activated adenosine triphosphatase (ATPase) of desensitized actomyosin by up to 60%. 2. The inhibitory activity of myofibrillar extracts and tropomyosin survives various agents known to denature proteins but to the action of which tropomyosin is unusually stable, namely heating at 100° and mild tryptic digestion. It is destroyed by prolonged treatment with trypsin. 3. The ethylenedioxybis-(ethyleneamino)tetra-acetic acid (EGTA)-sensitizing factor present in extracts of natural actomyosin and myofibrils could be selectively destroyed, leaving unchanged the inhibitory effect on the Ca2+-activated ATPase. There was no correlation between the EGTA-sensitizing and the Ca2+-activated inhibitory activities of tropomyosin prepared under different conditions. 4. Optimum inhibition was achieved when tropomyosin and the myosin of desensitized actomyosin were present in approximately equimolar proportions. Tropomyosin had no effect on the Ca2+-activated ATPase of myosin measured under similar conditions. 5. Evidence is presented showing that the tropomyosin binds to desensitized actomyosin under the conditions in which the ATPase is inhibited.

scholarly journals The regulatory proteins of the myofibril. Characterization and biological activity of the calcium-sensitizing factor (troponin A)

1972 ◽  
Vol 126 (1) ◽  
pp. 237-249 ◽  
Author(s):  
M. C. Schaub ◽  
S. V. Perry ◽  
W. Häcker
Keyword(s):  
Amino Acids ◽  
Biological Activity ◽  
Electrophoretic Mobility ◽  
Prolonged Exposure ◽  
Gel Filtration ◽  
Myofibrillar Protein ◽  
Inhibitory Factor ◽  
Regulatory Proteins ◽  
Protein System ◽  
Troponin Complex

1. Electrophoretically homogeneous calcium-sensitizing factor was prepared from the troponin complex by chromatography successively on sulphoethyl-Sephadex and on diethyl-(2-hydroxypropyl)aminoethyl-Sephadex in 6m-urea. It is a protein containing 53% of polar amino acids, of which a net excess consists of acidic residues. 2. On gel filtration the calcium-sensitizing factor was shown to be the only myofibrillar protein that bound 45Ca2+ tightly in the presence of 2–6m-urea. 3. Calcium-sensitizing factor effectively neutralized the effect of the inhibitory factor on the ATPase activities of actomyosin systems. Tropomyosin was essential for the regulation, by changes in the Ca2+ concentration, of the neutralizing effect of calcium-sensitizing factor on the inhibitory factor. 4. Prolonged exposure to chelators of Ca2+ produced an irreversibly modified form of calcium-sensitizing factor of higher electrophoretic mobility at pH8.6. The modified form neutralized the inhibitory factor action but this property could no longer be controlled by the Ca2+ concentration in the presence of tropomysin. 5. The calcium-sensitizing factor and tropomyosin could be replaced by their carboxymethylated derivatives in the relaxing-protein system.

scholarly journals Evidence from Insect Fibrillar Muscle about the Elementary Contractile Process

1967 ◽  
Vol 50 (6) ◽  
pp. 139-156 ◽  
Author(s):  
J. W. S. Pringle
Keyword(s):  
Ionic Strength ◽  
Atpase Activity ◽  
Striated Muscle ◽  
Contractile Activity ◽  
High Elasticity ◽  
Flight Muscles ◽  
The Cross ◽  
Cross Bridges ◽  
Low Ionic Strength ◽  
Water Bugs

Bundles of myofibrils prepared from the dorsal longitudinal flight muscles of giant water bugs show oscillatory contractile activity in solutions of low ionic strength containing ATP and 10-8-10-7 M Ca2+. This is due to delay between changes of length and changes of tension under activating conditions. The peculiarities of insect fibrillar muscle which give rise to this behavior are (1) the high elasticity of relaxed myofibrils, (2) a smaller degree of Ca2+ activation of ATPase activity in unstretched myofibrils and extracted actomyosin, and (3) a direct effect of stretch on ATPase activity. It is shown that the cross-bridges of striated muscle are probably formed from the heads of three myosin molecules and that in insect fibrillar muscle the cycles of mechanochemical energy conversion in the cross-bridges can be synchronized by imposed changes of length. This material is more suitable than vertebrate striated muscle for a study of the nature of the elementary contractile process.

Inhibitory Effect of Vitamin D2 on Adenosine-triphosphatase Activity

Nature ◽  
1966 ◽  
Vol 212 (5058) ◽  
pp. 203-204 ◽  
Author(s):  
V. B. SPIRICHEV ◽  
N. V. BLAZHEVICH
Keyword(s):  
Adenosine Triphosphatase ◽  
Inhibitory Effect ◽  
Vitamin D2 ◽  
Adenosine Triphosphatase Activity

Extractability and properties of the contractile proteins of vertebrate smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 169-181 ◽  
Keyword(s):  
Smooth Muscle ◽  
Ionic Strength ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Contractile Proteins ◽  
Biosynthetic Activity ◽  
Salting Out ◽  
Low Ionic Strength ◽  
The Comparative Study ◽  
Muscle Myosin

The vertebrate smooth muscles differ from the striated ones by their larger extracellular space, the smaller size of their cells and their high content in extracellular components. Furthermore, the smooth muscle cell is a bifunctional biological unit able to carry on also an important biosynthetic activity. The contractile proteins of vertebrate smooth muscle are extractable at low ionic strength contrarily to those of striated muscle. The partition of the salt extractable nitrogen between the low and high ionic strength extracts is very different in these two cases. Acidification of low ionic strength extracts of vertebrate smooth muscle at pH 5 allows precipitation of the contractile proteins quantitatively together with a large amount of contaminants typical of the smooth muscles. Comparison of the contractile proteins of vertebrate smooth muscle with their striated counterparts shows that actin is a very constant component of the contractile machinery, that tropomyosin holds an intermediate position, while myosin is the most variable. The smooth muscle myosin differs not only by some general properties as salting-out range and thermostability, but also by the behaviour of various parts of the molecule. The globular head has a different ATPase activity and is responsible for the very peculiar immunological behaviour of this myosin. The point along the myosin rod which is attacked by trypsin is much more resistant to proteolysis. The light meromyosin is more soluble and differs very much in amino acid composition. The comparative study of myosin reveals only minor variations from one species to the other but more or less wide ones within each species according to the type of muscle examined.

scholarly journals THE HISTOCHEMICAL DEMONSTRATION OF ADENOSINE TRIPHOSPHATASE ACTIVITY IN MYOCARDIUM

1964 ◽  
Vol 12 (10) ◽  
pp. 740-743 ◽  
Author(s):  
N. R. NILES ◽  
J. CHAYEN ◽  
G. J. CUNNINGHAM ◽  
LUCILLE BITENSKY
Keyword(s):  
Enzymatic Activity ◽  
Adenosine Triphosphate ◽  
Adenosine Triphosphatase ◽  
Inhibitory Effect ◽  
Histochemical Demonstration ◽  
Human Myocardium ◽  
Phosphate Esters ◽  
Precise Localization ◽  
Adenosine Triphosphatase Activity

Adenosine triphosphatase has been demonstrated histochemically in rat and human myocardium. To obtain its precise localization in discrete bands, apparently corresponding to the concentration of myosin, it was necessary to modify the existing technique to obtain better preservation of unfixed tissue and maximal enzymatic activity. Thus it was necessary to increase the concentration of calcium and to effect the reaction at pH 9.4 after treatment with 2:4-dinitrophenol. The specificity of the reaction was shown by these factors, by testing with phosphate esters other than adenosine triphosphate, and by the inhibitory effect of magnesium.

Effect of aldehyde fixatives on the adenosine phosphatases and ultrastructure of Vitreoscilla

1973 ◽  
Vol 19 (9) ◽  
pp. 1059-1064 ◽  
Author(s):  
Jeffrey C. Burnham ◽  
George J. Hageage Jr.
Keyword(s):  
Enzyme Inhibition ◽  
Microscopic Examination ◽  
Adenosine Triphosphatase ◽  
Osmium Tetroxide ◽  
Electron Microscopic Examination ◽  
Inhibitory Effect ◽  
Electron Microscopic ◽  
Adenosine Triphosphatase Activity ◽  
Enzymes Inhibition ◽  
Adenosine Phosphate

A variety of aldehydes used in electron cytochemistry including glutaraldehyde, glycidaldehyde, acetaldehyde, and methanol-free formaldehyde were examined for their inhibitory effect on the adenosine phosphate hydrolases of Vitreoscilla species. Enzyme inhibition increased with increasing aldehyde concentration. Of the aldehydes tested glycidaldehyde and acetaldehyde were least inhibitory for both adenosine diphosphatase and adenosine triphosphatase activity. Significantly, a 1% concentration of glutaraldehyde inhibited over 80% of the activity of both enzymes. Inhibition by all fixatives was variably decreased by the addition of 8% sucrose. Electron-microscopic examination of Vitreoscilla species fixed with the various aldehydes revealed that both acetaldehyde and glycidaldehyde followed by osmium tetroxide postfixation gave results comparable with glutaraldehyde–osmium tetroxide fixed cells.

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