scholarly journals Dense bodies and actin polarity in vertebrate smooth muscle.

1982 ◽  
Vol 95 (2) ◽  
pp. 403-413 ◽  
Author(s):  
M Bond ◽  
A V Somlyo
Keyword(s):  
Smooth Muscle ◽  
Vas Deferens ◽  
Dense Body ◽  
Thin Filaments ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1 ◽  
10 Nm Filaments ◽  
Rabbit Vas Deferens

The arrangement of cytoplasmic dense bodies in vertebrate smooth muscle and their relationship to the thin filaments was studied in cells from rabbit vas deferens and portal vein which were made hyperpermeable (skinned) with saponin and incubated with myosin subfragment 1 (S-1). The dense bodies were obliquely oriented, elongated structures sometimes appearing as chains up to 1.5 microns in length; they were often continuous across the cell for 200 to 300 nm and were interconnected by an oblique network of 10-nm filaments. The arrowheads, formed by S-1 decoration of actins, which inserted into both the sides and ends of dense bodies, always pointed away from the dense body, similar to the polarity of the thin filaments at the Z-bands of skeletal muscle. These results show that the cytoplasmic dense bodies function as anchoring sites for the thin filaments and indicate that the thin filaments, thick filaments, and dense bodies constitute a contractile unit.

Models of contractile units and their assembly in smooth muscle

2005 ◽  
Vol 83 (10) ◽  
pp. 825-831 ◽  
Author(s):  
Farah Ali ◽  
Peter D Paré ◽  
Chun Y Seow
Keyword(s):  
Smooth Muscle ◽  
Striated Muscle ◽  
Dense Body ◽  
Unit Length ◽  
Muscle Length ◽  
Thick Filament ◽  
Contractile Apparatus ◽  
Thin Filaments ◽  
Dense Bodies ◽  
In Series

It is believed that the contractile filaments in smooth muscle are organized into arrays of contractile units (similar to the sarcomeric structure in striated muscle), and that such an organization is crucial for transforming the mechanical activities of actomyosin interaction into cell shortening and force generation. Details of the filament organization, however, are still poorly understood. Several models of contractile filament architecture are discussed here. To account for the linear relationship observed between the force generated by a smooth muscle and the muscle length at the plateau of an isotonic contraction, a model of contractile unit is proposed. The model consists of 2 dense bodies with actin (thin) filaments attached, and a myosin (thick) filament lying between the parallel thin filaments. In addition, the thick filament is assumed to span the whole contractile unit length, from dense body to dense body, so that when the contractile unit shortens, the amount of overlap between the thick and thin filaments (i.e., the distance between the dense bodies) decreases in exact proportion to the amount of shortening. Assembly of the contractile units into functional contractile apparatus is assumed to involve a group of cells that form a mechanical syncytium. The contractile apparatus is assumed malleable in that the number of contractile units in series and in parallel can be altered to accommodate strains on the muscle and to maintain the muscle's optimal mechanical function.Key words: contraction model, ultrastructure, length adaptation, plasticity.

The influence of temperature on the thick filaments of vertebrate smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 197-202 ◽  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pigs ◽  
Taenia Coli ◽  
Thin Filaments ◽  
Influence Of Temperature ◽  
Thick Filaments ◽  
Influence Of Temperature On ◽  
10 Nm Filaments ◽  
Ion Analysis

When fixation of taenia coli from adult guinea-pigs is initiated at 37 °C only thin filaments and 10 nm filaments are preserved. At 37 °G (i.e. as in vivo ) thick filaments are very labile; to preserve them during fixation much thinner muscles must be used such as taenia coli from very young animals. The thick filaments from taenia coli of adult guinea-pigs can however be stabilized by pre-cooling the living muscles before fixation at 37 °C. An ion analysis of these muscles in vivo, and during fixation at 37 and 4 °C, showed that there is a K and Na ion exchange in the tissue both on cooling and during fixation; the exchange is most rapid on fixation particularly when it takes place at 37 °C. The Mg 2+ content appears to be unaffected by these conditions, but the Ca 2+ content rises both on cooling and during fixation (when the uptake is unexpectedly large). The selective destruction of the cell membrane is greatest when fixation is carried out at 37 °C. It is suggested that pre-cooling may alter thick filaments.

scholarly journals A filamentous cytoskeleton in vertebrate smooth muscle fibers.

1976 ◽  
Vol 68 (3) ◽  
pp. 539-556 ◽  
Author(s):  
P Cooke
Keyword(s):  
Molecular Weight ◽  
Smooth Muscle ◽  
Muscle Protein ◽  
Muscle Fibers ◽  
Thin Filaments ◽  
The Third ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Cell Fractions

There are three classes of myofilaments in vertebrate smooth muscle fibers. The thin filaments correspond to actin and the thick filaments are identified with myosin. The third class of myofilaments (100 A diam) is distinguished from both the actin and the myosin on the basis of fine structure, solubility, and pattern of localization in the muscle fibers. Direct structural evidence is presented to show that the 100A filament constitute an integrated filamentous network with the dense bodies in the sarcoplasm, and that they are not connected to either the actin or myosin filaments. Examination of (a) isolated dense bodies, (b) series of consecutive sections through the dense bodies, and (c) redistributed dense bodies in stretched muscle fibers supports this conclusion. It follows that the 100-A filaments complexes constitute a structrally distinct filamentous network. Analysis of polyacrylamide gels after electrophoresis of cell fractions that are enriched with respect to the 100-A filaments shows the presence of a new muscle protein with a molecular weight of 55,000. This protein can form filamentous segments that closely resemble in structure the native, isolated 100-A filaments. The results indicate that the filamentous network has a structure and composition that distinguish it from the actin and myosin in vertebrate smooth muscle.

scholarly journals THICK FILAMENTS IN VASCULAR SMOOTH MUSCLE

1971 ◽  
Vol 49 (3) ◽  
pp. 636-649 ◽  
Author(s):  
Carrick E. Devine ◽  
Andrew P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Actin Filaments ◽  
Vas Deferens ◽  
Average Diameter ◽  
Physiological Salt Solution ◽  
Taenia Coli ◽  
Striated Muscles ◽  
Thin Filaments ◽  
Thick Filaments

Two sets of myofilaments were demonstrated after incubation of strips of rabbit portal-anterior mesenteric vein under moderate stretch in a physiological salt solution. Thick filaments had a mean diameter of 18 nm and reached a maximum length of 1.4 µm with a mean length of 0.61 µm. In transverse sections, 2.5–5 nm particles were resolved as subunits of the thick filaments. Thin filaments had an average diameter of 8.4 nm and generally conformed to the structure believed to represent actin filaments in smooth and striated muscles. In the areas of maximum concentration there were 160–328 thick filaments/µm2 and the lowest ratio of thin to thick filaments was 12:1. Thick filaments were present in approximately equal numbers in vascular smooth muscle relaxed by theophylline, in Ca++-free solution, or contracted by norepinephrine. The same preparatory procedures used with vascular smooth muscle also enabled us to visualize thick filaments in guinea pig and rabbit taenia coli and vas deferens.

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 Regulation of the acto·myosin subfragment 1 interaction by troponin/tropomyosin. Evidence for control of a specific isomerization between two acto·myosin subfragment 1 states

1991 ◽  
Vol 279 (3) ◽  
pp. 711-718 ◽  
Author(s):  
D F A McKillop ◽  
M A Geeves
Keyword(s):  
Skeletal Muscle ◽  
Active Site ◽  
Actin Filaments ◽  
Thin Filaments ◽  
Closed State ◽  
Myosin Subfragment ◽  
Actomyosin Interaction ◽  
Binding Isotherms ◽  
Myosin Subfragment 1 ◽  
Site Binding

The co-operative binding of myosin subfragment 1 (S1) to reconstituted skeletal-muscle thin filaments has been examined by monitoring the fluorescence of a pyrene probe on Cys-374 of actin. The degree of co-operativity differs when phosphate, sulphate or ADP are bound to the S1 active site. Binding isotherms have been analysed according to the Geeves & Halsall [(1987) Biophys. J. 52, 215-220] model, which proposed that troponin and tropomyosin effected regulation of the actomyosin interaction by controlling an isomerization of the actomyosin complex. The data support the proposal that seven actin monomers associated with a single tropomyosin molecule act as a co-operative unit that can be in one of two states. In the ‘closed’ state myosin can bind to actin, but the subsequent isomerization is prevented. The isomerization is only allowed after the seven-actin unit is in the ‘open’ form. Ca2+ controls the proportion of actin filaments in the ‘closed’ and ‘open’ forms in the absence of myosin heads. The ratio of ‘closed’ to ‘open’ forms is approx. 50:1 in the absence of Ca2+ and 5:1 in its presence.

The dynamics of the interaction between myosin subfragment 1 and pyrene-labelled thin filaments, from rabbit skeletal muscle

1986 ◽  
Vol 229 (1254) ◽  
pp. 85-95 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Binding Affinity ◽  
Kinetic Studies ◽  
Rabbit Skeletal Muscle ◽  
Fluorescent Label ◽  
Weakly Bound ◽  
Thin Filaments ◽  
Fluorescence Titration ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1

We have used actin labelled in Cys–374 with N -(1-pyrenyl)iodoacetamide to monitor the dynamics and equilibria of the interaction between myosin subfragment 1 and the actin–troponin–tropomyosin complex in the presence of calcium. These results are compared with those obtained for pure actin and myosin subfragment 1. The sensitivity of this fluorescent label allowed us to measure the binding affinity of myosin subfragment 1 for actin directly by fluorescence titration. The affinity of subfragment 1 for actin is increased sixfold by troponin–tropomyosin in the presence of calcium. Kinetic studies of the interaction of subfragment 1 and actin have revealed an isomerization of the actin–subfragment 1 complex from a state in which actin is weakly bound ( K a = 5.9 x 10 4 M -1 ) to a more tightly bound complex ( K a = 1.7 x 10 7 M -1 ) (Coates, Criddle & Geeves (1985) Biochem. J. 232, 351). Results in the presence of troponin–tropomyosin show the same isomerization. The sixfold increase in affinity of subfragment 1 for actin is shown to be due to a decrease in the rate of dissociation of actin from the weakly bound complex.

scholarly journals A novel pressure-jump apparatus for the microvolume analysis of protein–ligand and protein–protein interactions: its application to nucleotide binding to skeletal-muscle and smooth-muscle myosin subfragment-1

2002 ◽  
Vol 366 (2) ◽  
pp. 643-651 ◽  
Author(s):  
David S. PEARSON ◽  
Georg HOLTERMANN ◽  
Patricia ELLISON ◽  
Christine CREMO ◽  
Michael A. GEEVES
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Protein Interactions ◽  
Muscle Protein ◽  
Smooth Muscles ◽  
High Volume ◽  
Pressure Jump ◽  
Original Design ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1

Reactions involving proteins frequently involve large changes in volume, which allows the equilibrium position to be perturbed by changes in pressure. Rapid changes in pressure can thus be used to initiate relaxation in pressure; however, this approach is seldom used, because it requires specialized equipment. We have built a microvolume (50μl) pressure-jump apparatus, powered by a piezoelectric actuator, based on the original design of Clegg and Maxfield [(1976) Rev. Sci. Instrum. 47, 1383–1393]. This equipment can apply pressure changes of ±20MPa (maximally) in time periods as short as 80μs and follow the resulting change in fluorescence signals. The system is relatively simple to use with fast (approx. 1min) exchange of samples. In the present study, we show that this system can perturb the binding of 2′(3′)-O-(N-methylanthraniloyl)-ADP to myosin subfragment-1(S1) from skeletal and smooth muscles. The kinetic data are consistent with previous work, and in addition show that, although 2′(3′)-O-(N-methylanthraniloyl)-ADP binds with a similar affinity to both proteins, the increase in molar volume for the skeletal-muscle S1 binding to ADP is half of that for the smooth-muscle protein. This high-volume change for smooth-muscle S1 may be related to the ability of ADP to induce a 23° tilt in the tail of S1 bound to actin.

scholarly journals Molecular Mechanisms of Muscle Weakness Associated with E173A Mutation in Tpm3.12. Troponin Ca2+ Sensitivity Inhibitor W7 Can Reduce the Damaging Effect of This Mutation

2020 ◽  
Vol 21 (12) ◽  
pp. 4421
Author(s):  
Yurii S. Borovikov ◽  
Armen O. Simonyan ◽  
Stanislava V. Avrova ◽  
Vladimir V. Sirenko ◽  
Charles S. Redwood ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Muscle Weakness ◽  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Spatial Arrangement ◽  
Muscle Fibres ◽  
Thin Filaments ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1

Substitution of Ala for Glu residue in position 173 of γ-tropomyosin (Tpm3.12) is associated with muscle weakness. Here we observe that this mutation increases myofilament Ca2+-sensitivity and inhibits in vitro actin-activated ATPase activity of myosin subfragment-1 at high Ca2+. In order to determine the critical conformational changes in myosin, actin and tropomyosin caused by the mutation, we used the technique of polarized fluorimetry. It was found that this mutation changes the spatial arrangement of actin monomers and myosin heads, and the position of the mutant tropomyosin on the thin filaments in muscle fibres at various mimicked stages of the ATPase cycle. At low Ca2+ the E173A mutant tropomyosin shifts towards the inner domains of actin at all stages of the cycle, and this is accompanied by an increase in the number of switched-on actin monomers and myosin heads strongly bound to F-actin even at relaxation. Contrarily, at high Ca2+ the amount of the strongly bound myosin heads slightly decreases. These changes in the balance of the strongly bound myosin heads in the ATPase cycle may underlie the occurrence of muscle weakness. W7, an inhibitor of troponin Ca2+-sensitivity, restores the increase in the number of myosin heads strongly bound to F-actin at high Ca2+ and stops their strong binding at relaxation, suggesting the possibility of using Ca2+-desensitizers to reduce the damaging effect of the E173A mutation on muscle fibre contractility.

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