scholarly journals Substructure and accessory proteins in scallop myosin filaments.

1989 ◽  
Vol 109 (2) ◽  
pp. 539-547 ◽  
Author(s):  
P Vibert ◽  
L Castellani
Keyword(s):  
Ionic Strength ◽  
Striated Muscle ◽  
Rotational Symmetry ◽  
Thick Filament ◽  
Accessory Proteins ◽  
Myosin Filaments ◽  
Cross Bridges ◽  
Low Ionic Strength ◽  
Muscle Myosin

Native myosin filaments from scallop striated muscle fray into subfilaments of approximately 100-A diameter when exposed to solutions of low ionic strength. The number of subfilaments appears to be five to seven (close to the sevenfold rotational symmetry of the native filament), and the subfilaments probably coil around one another. Synthetic filaments assembled from purified scallop myosin at roughly physiological ionic strength have diameters similar to those of native filaments, but are much longer. They too can be frayed into subfilaments at low ionic strength. Synthetic filaments share what may be an important regulatory property with native filaments: an order-disorder transition in the helical arrangement of myosin cross-bridges that is induced on activation by calcium, removal of nucleotide, or modification of a myosin head sulfhydryl. Some native filaments from scallop striated muscle carry short "end filaments" protruding from their tips, comparable to the structures associated with vertebrate striated muscle myosin filaments. Gell electrophoresis of scallop muscle homogenates reveals the presence of high molecular weight proteins that may include the invertebrate counterpart of titin, a component of the vertebrate end filament. Although the myosin molecule itself may contain much of the information required to direct its assembly, other factors acting in vivo, including interactions with accessory proteins, probably contribute to the assembly of a precisely defined thick filament during myofibrillogenesis.

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 LOCALIZATION OF MYOSIN FILAMENTS IN SMOOTH MUSCLE

1968 ◽  
Vol 37 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Robert E. Kelly ◽  
Robert V. Rice
Keyword(s):  
Smooth Muscle ◽  
Cross Section ◽  
Striated Muscle ◽  
Thick Filament ◽  
Longitudinal Axis ◽  
Thin Filaments ◽  
Chicken Gizzard ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Muscle Myosin

Thick myosin filaments, in addition to actin filaments, were found in sections of glycerinated chicken gizzard smooth muscle when fixed at a pH below 6.6. The thick filaments were often grouped into bundles and run in the longitudinal axis of the smooth muscle cell. Each thick filament was surrounded by a number of thin filaments, giving the filament arrangement a rosette appearance in cross-section. The exact ratio of thick filaments to thin filaments could not be determined since most arrays were not so regular as those commonly found in striated muscle. Some rosettes had seven or eight thin filaments surrounding a single thick filament. Homogenates of smooth muscle of chicken gizzard also showed both thick and thin filaments when the isolation was carried out at a pH below 6.6, but only thin filaments were found at pH 7.4. No Z or M lines were observed in chicken gizzard muscle containing both thick and thin filaments. The lack of these organizing structures may allow smooth muscle myosin to disaggregate readily at pH 7.4.

scholarly journals Assembly of smooth muscle myosin into side-polar filaments.

1977 ◽  
Vol 75 (3) ◽  
pp. 990-996 ◽  
Author(s):  
R Craig ◽  
J Megerman
Keyword(s):  
Smooth Muscle ◽  
Opposite Polarity ◽  
Skeletal Muscle Myosin ◽  
Myosin Filaments ◽  
Skeletal Myosin ◽  
Cross Bridges ◽  
Bipolar Filament ◽  
Muscle Myosin

The in vitro assembly of myosin purified from calf aorta muscle has been studied by electron microscopy. Two types of filament are formed: short bipolar filament similar to those formed from skeletal muscle myosin, and longer "side-polar" filaments having cross bridges with a single polarity along the entire length of one side and the opposite polarity along the other side. Unlike the case with skeletal myosin filaments, antiparallel interactions between myosin molecules occur along the whole length of side-polar filaments. The side-polar structure may be related to the in vivo form of myosin in vertebrate smooth muscle.

scholarly journals Hydrophobicity variations along the surface of the coiled-coil rod may mediate striated muscle myosin assembly in Caenorhabditis elegans.

1996 ◽  
Vol 135 (2) ◽  
pp. 371-382 ◽  
Author(s):  
P E Hoppe ◽  
R H Waterston
Keyword(s):  
Caenorhabditis Elegans ◽  
Striated Muscle ◽  
Coiled Coil ◽  
Thick Filament ◽  
Surface Hydrophobicity ◽  
Filament Assembly ◽  
Thick Filaments ◽  
Characteristic Variation ◽  
Muscle Myosin

Caenorhabditis elegans body wall muscle contains two isoforms of myosin heavy chain, MHC A and MHC B, that differ in their ability to initiate thick filament assembly. Whereas mutant animals that lack the major isoform, MHC B, have fewer thick filaments, mutant animals that lack the minor isoform, MHC A, contain no normal thick filaments. MHC A, but not MHC B, is present at the center of the bipolar thick filament where initiation of assembly is thought to occur (Miller, D.M.,I. Ortiz, G.C. Berliner, and H.F. Epstein. 1983. Cell. 34:477-490). We mapped the sequences that confer A-specific function by constructing chimeric myosins and testing them in vivo. We have identified two distinct regions of the MHC A rod that are sufficient in chimeric myosins for filament initiation function. Within these regions, MHC A displays a more hydrophobic rod surface, making it more similar to paramyosin, which forms the thick filament core. We propose that these regions play an important role in filament initiation, perhaps mediating close contacts between MHC A and paramyosin in an antiparallel arrangement at the filament center. Furthermore, our analysis revealed that all striated muscle myosins show a characteristic variation in surface hydrophobicity along the length of the rod that may play an important role in driving assembly and determining the stagger at which dimers associate.

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.

scholarly journals Structural changes induced in Ca2+-regulated myosin filaments by Ca2+ and ATP.

1989 ◽  
Vol 109 (2) ◽  
pp. 529-538 ◽  
Author(s):  
L L Frado ◽  
R Craig
Keyword(s):  
Structural Changes ◽  
Striated Muscle ◽  
Structural Basis ◽  
Ordered Structure ◽  
Compact Structure ◽  
Crude Homogenate ◽  
Myosin Filaments ◽  
The Cross ◽  
Cross Bridges ◽  
Muscle Myosin

We have used electron microscopy and proteolytic susceptibility to study the structural basis of myosin-linked regulation in synthetic filaments of scallop striated muscle myosin. Using papain as a probe of the structure of the head-rod junction, we find that this region of myosin is approximately five times more susceptible to proteolytic attack under activating (ATP/high Ca2+) or rigor (no ATP) conditions than under relaxing conditions (ATP/low Ca2+). A similar result was obtained with native myosin filaments in a crude homogenate of scallop muscle. Proteolytic susceptibility under conditions in which ADP or adenosine 5'-(beta, gamma-imidotriphosphate) (AMPPNP) replaced ATP was similar to that in the absence of nucleotide. Synthetic myosin filaments negatively stained under relaxing conditions showed a compact structure, in which the myosin cross-bridges were close to the filament backbone and well ordered, with a clear 14.5-nm axial repeat. Under activating or rigor conditions, the cross-bridges became clumped and disordered and frequently projected further from the filament backbone, as has been found with native filaments; when ADP or AMPPNP replaced ATP, the cross-bridges were also disordered. We conclude (a) that Ca2+ and ATP affect the affinity of the myosin cross-bridges for the filament backbone or for each other; (b) that the changes observed in the myosin filaments reflect a property of the myosin molecules alone, and are unlikely to be an artifact of negative staining; and (c) that the ordered structure occurs only in the relaxed state, requiring both the presence of hydrolyzed ATP on the myosin heads and the absence of Ca2+.

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.

The self-assembly of synthetic filaments of myosin isolated from Chaos carolinensis and Amoeba proteus

1977 ◽  
Vol 25 (1) ◽  
pp. 387-402
Author(s):  
J.S. Condeelis
Keyword(s):  
Ionic Strength ◽  
Self Assembly ◽  
Divalent Cations ◽  
Central Zone ◽  
Thick Filament ◽  
Amoeba Proteus ◽  
High Ionic Strength ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Low Ionic Strength

Synthetic myosin thick filaments were formed from preparations of electrophoretically homogeneous myosin isolated from Chaos carolinensis and Amoeba proteus when dialysed to physiological ionic strength and pH. Myosin dialysed directly against low ionic strength buffers formed native-like thick filaments in the presence and absence of exogenous divalent cations. The average dimensions of the synthetic filaments grown under these conditions were 455 nm long and 16 nm wide with a distinct bare central zone 174 nm long. Myosin predialysed against EGTA-EDTA solutions at high ionic strength and then dialysed to low ionic strength formed native-like filaments only in the presence of 1mM Mg2+. 1 mM Ca2+ could not be substituted for Mg2+ under these conditions to achieve native-like filaments. Filaments grown from predialysed myosin in the absence of Mg2+ resembled EGTA-dissociated myosin filaments observed in EGTA-treated cytoplasm and were highly branched, poorly formed filaments lacking a distinct bare central zone. The average dimensions of the filaments grown from predialysed myosin in the absence of Mg2+ were 328 nm long, 13 nm wide with a bare central zone 111 nm long. Under the conditions tested, myosin isolated from these amoebae did not demonstrate a divalent cation requirement for thick filament formation. The results obtained with myosin isolated from the 2 organisms were identical.

scholarly journals A Region of the Myosin Rod Important for Interaction With Paramyosin in Caenorhabditis elegans Striated Muscle

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 631-643
Author(s):  
Pamela E Hoppe ◽  
Robert H Waterston
Keyword(s):  
Caenorhabditis Elegans ◽  
Heavy Chain ◽  
Molecular Interaction ◽  
Striated Muscle ◽  
Genetic Interaction ◽  
Specific Interaction ◽  
Thick Filament ◽  
Parallel Arrangement ◽  
Myosin Rod

Abstract The precise arrangement of molecules within the thick filament, as well as the mechanisms by which this arrangement is specified, remains unclear. In this article, we have exploited a unique genetic interaction between one isoform of myosin heavy chain (MHC) and paramyosin in Caenorhabditis elegans to probe the molecular interaction between MHC and paramyosin in vivo. Using chimeric myosin constructs, we have defined a 322-residue region of the MHC A rod critical for suppression of the structural and motility defects associated with the unc-15(e73) allele. Chimeric constructs lacking this region of MHC A either fail to suppress, or act as dominant enhancers of, the e73 phenotype. Although the 322-residue region is required for suppression activity, our data suggest that sequences along the length of the rod also play a role in the isoform-specific interaction between MHC A and paramyosin. Our genetic and cell biological analyses of construct behavior suggest that the 322-residue region of MHC A is important for thick filament stability. We present a model in which this region mediates an avid interaction between MHC A and paramyosin in parallel arrangement in formation of the filament arms.

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