Ultrastructure of the Striated Muscle of the Scallop (Placopecten magellanicus)

1968 ◽  
Vol 25 (7) ◽  
pp. 1339-1345 ◽  
Author(s):  
C. M. Morrison ◽  
P. H. Odense
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Adductor Muscle ◽  
Myosin Filament ◽  
Placopecten Magellanicus

The striated adductor muscle of the scallop Placopecten magellanicus is described. The fusiform uninucleate cells contain one fibril which is divided into A and I zones, and has Z and H bands. The A zone is 1.9 μ long, and in this zone apart from the H band about eight actin filaments surround each myosin filament. A sarcoplasmic reticulum envelops the fibril. Tubules of this reticulum are mainly oriented longitudinally and swellings from dyads with the sarcolemma.

The Ultrastructure of the White Striated Myotomal Muscle of the Cod, Gadus morhua

1967 ◽  
Vol 24 (12) ◽  
pp. 2549-2553 ◽  
Author(s):  
C. M. Bishop ◽  
P. H. Odense
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Cross Section ◽  
Actin Filaments ◽  
Gadus Morhua ◽  
Striated Muscle ◽  
Fish Muscle ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Myotomal Muscle

The structure of the white skeletal muscle of the cod (Gadus morhua) is described. The peripheral fibrils are ribbon-like and rectangular in cross section with the long axis normal to the sarcolemma. The inner fibrils are mainly polygonal in cross section. Most of the mitochondria and nuclei are peripheral to the fibrils and next to the sarcolemma. The arrangement of the contractile proteins is typical for striated muscle, and the sarcoplasmic reticulum and transverse tubular system are similar to those in other white skeletal fish muscle. A distinct N-band is apparent with indications of branching and reorientation of the actin filaments. Mitochondria are often closely associated with the Z line.

Structure of Myosin Subfragment-1 from Electron Microscopy and Crystallography

1988 ◽  
Vol 46 ◽  
pp. 156-157
Author(s):  
Donald A. Winkelmann
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Actin Filaments ◽  
Light Chains ◽  
Myosin Filament ◽  
Primary Role ◽  
Heavy Chains ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1 ◽  
Globular Head

The primary role of the interaction of actin and myosin is the generation of force and motion as a direct consequence of the cyclic interaction of myosin crossbridges with actin filaments. Myosin is composed of six polypeptides: two heavy chains of molecular weight 220,000 daltons and two pairs of light chains of molecular weight 17,000-23,000. The C-terminal portions of the myosin heavy chains associate to form an α-helical coiled-coil rod which is responsible for myosin filament formation. The N-terminal portion of each heavy chain associates with two different light chains to form a globular head that binds actin and hydrolyses ATP. Myosin can be fragmented by limited proteolysis into several structural and functional domains. It has recently been demonstrated using an in vitro movement assay that the globular head domain, subfragment-1, is sufficient to cause sliding movement of actin filaments.The discovery of conditions for crystallization of the myosin subfragment-1 (S1) has led to a systematic analysis of S1 structure by x-ray crystallography and electron microscopy. Image analysis of electron micrographs of thin sections of small S1 crystals has been used to determine the structure of S1 in the crystal lattice.

Orientation of actin filaments during motion in motility assay

1995 ◽  
Vol 53 ◽  
pp. 52-53
Author(s):  
J. Borejdo ◽  
S. Burlacu
Keyword(s):  
Actin Filaments ◽  
Thin Filament ◽  
Striated Muscle ◽  
Myosin Head ◽  
Classical Method ◽  
Polarization Of Fluorescence ◽  
Single Protein ◽  
Intracellular Organelles ◽  
Change Orientation ◽  
Active Entity

Polarization of fluorescence is a classical method to assess orientation or mobility of macromolecules. It has been a common practice to measure polarization of fluorescence through a microscope to characterize orientation or mobility of intracellular organelles, for example anisotropic bands in striated muscle. Recently, we have extended this technique to characterize single protein molecules. The scientific question concerned the current problem in muscle motility: whether myosin heads or actin filaments change orientation during contraction. The classical view is that the force-generating step in muscle is caused by change in orientation of myosin head (subfragment-1 or SI) relative to the axis of thin filament. The molecular impeller which causes this change resides at the interface between actin and SI, but it is not clear whether only the myosin head or both SI and actin change orientation during contraction. Most studies assume that observed orientational change in myosin head is a reflection of the fact that myosin is an active entity and actin serves merely as a passive "rail" on which myosin moves.

scholarly journals Single turnovers of fluorescent ATP bound to bipolar myosin filament during actin filaments sliding

BIOPHYSICS ◽  
2013 ◽  
Vol 9 (0) ◽  
pp. 13-20
Author(s):  
Takahiro Maruta ◽  
Takahiro Kobatake ◽  
Hiroyuki Okubo ◽  
Shigeru Chaen
Keyword(s):  
Actin Filaments ◽  
Myosin Filament

scholarly journals QUANTITATIVE AND HISTOCHEMICAL STUDIES ON THE DESORPTION AND READSORPTION OF ALDOLASE IN CROSS-STRIATED MUSCLE

1969 ◽  
Vol 17 (5) ◽  
pp. 314-320 ◽  
Author(s):  
H. ARNOLD ◽  
J. NOLTE ◽  
D. PETTE
Keyword(s):  
Enzyme Activity ◽  
Actin Filaments ◽  
Phosphate Buffer ◽  
Striated Muscle ◽  
Psoas Muscle ◽  
Histochemical Staining ◽  
Intracellular Location ◽  
Successive Extraction ◽  
Complete Extraction

Complete extraction of aldolase from minced rabbit psoas muscle was achieved by successive extraction steps in 0.1 M phosphate buffer. Aldolase was then readsorbed quantitatively to the depleted myofibrils. Extraction, readsorption and a final redsorption of the enzyme were followed quantitatively by enzyme activity determinations and qualitatively by histochemical staining of aldolase. The intracellular location of the readsorbed enzyme was found to be identical with that of aldolase in native muscle. In both cases, aldolase was localized within the isotropic bands. These results as well as the previously demonstrated binding of the enzyme to F-actin suggest that aldolase is located within the interfilamentary sarcoplasm of the isotropic bands and is probably also bound in vivo to the actin filaments.

scholarly journals Tropomodulin caps the pointed ends of actin filaments.

1994 ◽  
Vol 127 (6) ◽  
pp. 1627-1635 ◽  
Author(s):  
A Weber ◽  
C R Pennise ◽  
G G Babcock ◽  
V M Fowler
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Critical Concentration ◽  
Thin Filaments ◽  
Capping Protein ◽  
End Capping ◽  
Pointed End ◽  
A Site

Many proteins have been shown to cap the fast growing (barbed) ends of actin filaments, but none have been shown to block elongation and depolymerization at the slow growing (pointed) filament ends. Tropomodulin is a tropomyosin-binding protein originally isolated from red blood cells that has been localized by immunofluorescence staining to a site at or near the pointed ends of skeletal muscle thin filaments (Fowler, V. M., M. A., Sussman, P. G. Miller, B. E. Flucher, and M. P. Daniels. 1993. J. Cell Biol. 120: 411-420). Our experiments demonstrate that tropomodulin in conjunction with tropomyosin is a pointed end capping protein: it completely blocks both elongation and depolymerization at the pointed ends of tropomyosin-containing actin filaments in concentrations stoichiometric to the concentration of filament ends (Kd < or = 1 nM). In the absence of tropomyosin, tropomodulin acts as a "leaky" cap, partially inhibiting elongation and depolymerization at the pointed filament ends (Kd for inhibition of elongation = 0.1-0.4 microM). Thus, tropomodulin can bind directly to actin at the pointed filament end. Tropomodulin also doubles the critical concentration at the pointed ends of pure actin filaments without affecting either the rate of extent of polymerization at the barbed filament ends, indicating that tropomodulin does not sequester actin monomers. Our experiments provide direct biochemical evidence that tropomodulin binds to both the terminal tropomyosin and actin molecules at the pointed filament end, and is the long sought-after pointed end capping protein. We propose that tropomodulin plays a role in maintaining the narrow length distributions of the stable, tropomyosin-containing actin filaments in striated muscle and in red blood cells.

scholarly journals Tracking the sarcoplasmic reticulum membrane voltage in muscle with a FRET biosensor

2018 ◽  
Vol 150 (8) ◽  
pp. 1163-1177 ◽  
Author(s):  
Colline Sanchez ◽  
Christine Berthier ◽  
Bruno Allard ◽  
Jimmy Perrot ◽  
Clément Bouvard ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Voltage Clamp ◽  
Ryanodine Receptor ◽  
Striated Muscle ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Membrane Voltage ◽  
Voltage Sensitivity ◽  
Cell Functions

Ion channel activity in the plasma membrane of living cells generates voltage changes that are critical for numerous biological functions. The membrane of the endoplasmic/sarcoplasmic reticulum (ER/SR) is also endowed with ion channels, but whether changes in its voltage occur during cellular activity has remained ambiguous. This issue is critical for cell functions that depend on a Ca2+ flux across the reticulum membrane. This is the case for contraction of striated muscle, which is triggered by opening of ryanodine receptor Ca2+ release channels in the SR membrane in response to depolarization of the transverse invaginations of the plasma membrane (the t-tubules). Here, we use targeted expression of voltage-sensitive fluorescence resonance energy transfer (FRET) probes of the Mermaid family in differentiated muscle fibers to determine whether changes in SR membrane voltage occur during depolarization–contraction coupling. In the absence of an SR targeting sequence, FRET signals from probes present in the t-tubule membrane allow calibration of the voltage sensitivity and amplitude of the response to voltage-clamp pulses. Successful SR targeting of the probes was achieved using an N-terminal domain of triadin, which completely eliminates voltage-clamp–activated FRET signals from the t-tubule membrane of transfected fibers. In fibers expressing SR-targeted Mermaid probes, activation of SR Ca2+ release in the presence of intracellular ethyleneglycol-bis(β-amino-ethyl ether)-N,N,N′,N′-tetra acetic acid (EGTA) results in an accompanying FRET signal. We find that this signal results from pH sensitivity of the probe, which detects cytosolic acidification because of the release of protons upon Ca2+ binding to EGTA. When EGTA is substituted with either 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid or the contraction blocker N-benzyl-p-toluene sulfonamide, we find no indication of a substantial change in the FRET response caused by a voltage change. These results suggest that the ryanodine receptor–mediated SR Ca2+ efflux is well balanced by concomitant counterion currents across the SR membrane.

Characterization of the actin filament capping state in human erythrocyte ghost and cytoskeletal preparations

2000 ◽  
Vol 349 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Philip A. KUHLMAN
Keyword(s):  
Actin Filament ◽  
Human Erythrocyte ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Length Distribution ◽  
Shearing Stress ◽  
Bivalent Cation ◽  
Thin Filaments ◽  
Cation Concentration ◽  
Bivalent Cations

The narrow Gaussian-length-distribution of actin filaments forming the cytoskeleton of the human erythrocyte indicates the existence of strict mechanisms for length determination and maintenance. A similar regulation is achieved in striated muscle by the capping of both the ends of the thin filaments, which consequently prevents monomer exchange. However, the ability of erythroid cytoskeletal preparations to nucleate actin polymerization has led to the proliferation of the idea that at least the barbed ends of the actin filaments are uncapped. The mechanism by which the length of the filaments is thus maintained has been left open to debate. In an effort to resolve any doubt regarding length-maintenance in human erythrocytes we have characterized the capping state of the actin filaments in a number of different ghost and cytoskeletal preparations. Under conditions of sufficiently high bivalent-cation concentration the actin filaments retain functional caps at both the barbed and pointed ends. Hence filament capping at both ends prevents redistribution of the actin monomer in a similar manner to that proposed for the thin filaments of striated muscle. Actin filament uncapping is apparently caused by the centrifugal shearing stress imposed during ghost preparation. The uncapping is more pronounced when the bivalent-cation concentration is reduced or when the membrane is removed by detergents. The effects of bivalent cations seem to be mediated through the erythroid protein spectrin, consistent with the hypothesis of Wallis et al. [Wallis, Babitch and Wenegieme (1993) Biochemistry 32, 5045-5050] that the ability of spectrin to resist shearing stress is dependent on the degree of bound bivalent cations.

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