scholarly journals INTRINSIC BIREFRINGENCE OF GLYCERINATED MYOFIBRILS

1971 ◽  
Vol 51 (3) ◽  
pp. 763-771 ◽  
Author(s):  
Richard H. Colby
Keyword(s):  
Thin Filament ◽  
Striated Muscle ◽  
Thick Filament ◽  
Weight Basis ◽  
Macromolecular Structure ◽  
Form Birefringence ◽  
Sliding Filament Theory ◽  
Filament Protein ◽  
Formalin Fixed ◽  
Intrinsic Birefringence

Patterns of intrinsic birefringence were revealed in formalin-fixed, glycerinated myofibrils from rabbit striated muscle, by perfusing them with solvents of refractive index near to that of protein, about 1.570. The patterns differ substantially from those obtained in physiological salt solutions, due to the elimination of edge- and form birefringence. Analysis of myofibrils at various stages of shortening has produced results fully consistent with the sliding filament theory of contraction. On a weight basis, the intrinsic birefringence of thick-filament protein is about 2.4 times that of thin-filament protein. Nonadditivity of thick- and thin-filament birefringence in the overlap regions of A bands may indicate an alteration of macromolecular structure due to interaction between the two types of filaments.

scholarly journals Specific Myosin Heavy Chain Mutations Suppress Troponin I Defects in Drosophila Muscles

1999 ◽  
Vol 144 (5) ◽  
pp. 989-1000 ◽  
Author(s):  
William A. Kronert ◽  
Angel Acebes ◽  
Alberto Ferrús ◽  
Sanford I. Bernstein
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Thin Filament ◽  
Troponin I ◽  
Point Mutations ◽  
Thick Filament ◽  
Actin Binding ◽  
Filament Protein ◽  
Phenotypic Rescue

We show that specific mutations in the head of the thick filament molecule myosin heavy chain prevent a degenerative muscle syndrome resulting from the hdp2 mutation in the thin filament protein troponin I. One mutation deletes eight residues from the actin binding loop of myosin, while a second affects a residue at the base of this loop. Two other mutations affect amino acids near the site of nucleotide entry and exit in the motor domain. We document the degree of phenotypic rescue each suppressor permits and show that other point mutations in myosin, as well as null mutations, fail to suppress the hdp2 phenotype. We discuss mechanisms by which the hdp2 phenotypes are suppressed and conclude that the specific residues we identified in myosin are important in regulating thick and thin filament interactions. This in vivo approach to dissecting the contractile cycle defines novel molecular processes that may be difficult to uncover by biochemical and structural analysis. Our study illustrates how expression of genetic defects are dependent upon genetic background, and therefore could have implications for understanding gene interactions in human disease.

scholarly journals IMMUNOHISTOCHEMICAL LOCALIZATION OF CONTRACTILE PROTEINS IN LIMULUS STRIATED MUSCLE

1972 ◽  
Vol 55 (1) ◽  
pp. 221-235 ◽  
Author(s):  
Rhea J. C. Levine ◽  
Maynard M. Dewey ◽  
George W. de Villafranca
Keyword(s):  
Thin Filament ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Fluorescent Antibody ◽  
Thick Filament ◽  
Immunohistochemical Localization ◽  
Differential Staining ◽  
Indirect Fluorescent Antibody ◽  
The Core ◽  
Lateral Margins

Limulus paramyosin and myosin were localized in the A bands of glycerinated Limulus striated muscle by the indirect horseradish peroxidase-labeled antibody and direct and indirect fluorescent antibody techniques. Localization of each protein in the A band varied with sarcomere length. Antiparamyosin was bound at the lateral margins of the A bands in long (∼ 10.0 µ) and intermediate (∼ 7.0 µ) length sarcomeres, and also in a thin line in the central A bands of sarcomeres, 7.0–∼6.0 µ. Antiparamyosin stained the entire A bands of short sarcomeres (<6.0). Conversely, antimyosin stained the entire A bands of long sarcomeres, showed decreased intensity of central A band staining except for a thin medial line in intermediate length sarcomeres, and was bound only in the lateral A bands of short sarcomeres. These results are consistent with a model in which paramyosin comprises the core of the thick filament and myosin forms a cortex. Differential staining observed using antiparamyosin and antimyosin at various sarcomere lengths and changes in A band lengths reflect the extent of thick-thin filament interaction and conformational change in the thick filament during sarcomeric shortening.

scholarly journals Nature and origin of gap filaments in striated muscle

1991 ◽  
Vol 100 (4) ◽  
pp. 809-814 ◽  
Author(s):  
K. Trombitas ◽  
P.H. Baatsen ◽  
M.S. Kellermayer ◽  
G.H. Pollack
Keyword(s):  
Thin Filament ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Thick Filament ◽  
Abrupt Increase ◽  
Semitendinosus Muscle ◽  
Thin Filaments ◽  
Filament System ◽  
Anchor Points ◽  
High Degree

Immunoelectron microscopy was used to study the nature and origin of ‘gap’ filaments in frog semitendinosus muscle. Gap filaments are fine longitudinal filaments observable only in sarcomeres stretched beyond thick/thin filament overlap: they occupy the gap between the tips of thick and thin filaments. To test whether the gap filaments are part of the titin-filament system, we employed monoclonal antibodies to titin (T-11, Sigma) and observed the location of the epitope at a series of sarcomere lengths. At resting sarcomere length, the epitope was positioned in the I-band approximately 50 nm beyond the apparent ends of the thick filament. The location did not change perceptibly with increasing sarcomere length up to 3.6 microns. Above 3.6 microns, the span between the epitope and the end of the A-band abruptly increased, and above 4 microns, the antibodies could be seen to decorate the gap filaments. Between 5 and 6 microns, the epitope remained approximately in the middle of the gap. Even with this high degree of stretch, the label remained more or less aligned across the myofibril. The abrupt increase of span beyond 3.6 microns implies that the A-band domain of titin is pulled free of its anchor points along the thick filament, and moves toward the gap. Although this domain is functionally inextensible at physiological sarcomere length, the epitope movement in extremely stretched muscle shows that it is intrinsically elastic. Thus, the evidence confirms that gap filaments are clearly part of the titin-filament system. They are derived not only from the I-band domain of titin, but also from its A-band domain.

scholarly journals Titin switches from an extensible spring to a mechanical rectifier upon muscle activation

2021 ◽  
Author(s):  
Caterina Squarci ◽  
Pasquale Bianco ◽  
Massimo Reconditi ◽  
Marco Caremani ◽  
Theyencheri Narayanan ◽  
...  
Keyword(s):  
Thin Filament ◽  
Muscle Activation ◽  
Striated Muscle ◽  
Thick Filament ◽  
Frog Muscle ◽  
Motor Responses ◽  
Filament Activation ◽  
Single Fibres ◽  
Myosin Motors ◽  
Stimulation Of

In contracting striated muscle titin acts as a spring in parallel with the array of myosin motors in each half-sarcomere and could prevent the intrinsic instability of thousands of serially linked half-sarcomeres, if its stiffness, at physiological sarcomere lengths (SL), were ten times larger than reported. Here we define titin mechanical properties during tetanic stimulation of single fibres of frog muscle by suppressing myosin motor responses with Para-Nitro-Blebbistatin, which is able to freeze thick filament in the resting state. We discover that thin filament activation switches I-band titin spring from the large SL-dependent extensibility of the OFF-state to an ON-state in which titin acts as a SL-independent mechanical rectifier, allowing free shortening while opposing stretch with an effective stiffness 4 pN nm-1 per half-thick filament. In this way during contraction titin limits weak half-sarcomere elongation to a few % and, also, provides an efficient link for mechanosensing-based thick filament activation.

scholarly journals Aberrant myofibril assembly in tropomodulin1 null mice leads to aborted heart development and embryonic lethality

2003 ◽  
Vol 163 (5) ◽  
pp. 1033-1044 ◽  
Author(s):  
Kimberly L. Fritz-Six ◽  
Patrick R. Cox ◽  
Robert S. Fischer ◽  
Bisong Xu ◽  
Carol C. Gregorio ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Heart Development ◽  
Knockout Mouse ◽  
Thin Filament ◽  
Striated Muscle ◽  
Heart Defects ◽  
Thick Filament ◽  
Embryonic Lethality ◽  
Actin Dynamics ◽  
Filament Assembly

Tropomodulin1 (Tmod1) caps thin filament pointed ends in striated muscle, where it controls filament lengths by regulating actin dynamics. Here, we investigated myofibril assembly and heart development in a Tmod1 knockout mouse. In the absence of Tmod1, embryonic development appeared normal up to embryonic day (E) 8.5. By E9.5, heart defects were evident, including aborted development of the myocardium and inability to pump, leading to embryonic lethality by E10.5. Confocal microscopy of hearts of E8–8.5 Tmod1 null embryos revealed structures resembling nascent myofibrils with continuous F-actin staining and periodic dots of α-actinin, indicating that I-Z-I complexes assembled in the absence of Tmod1. Myomesin, a thick filament component, was also assembled normally along these structures, indicating that thick filament assembly is independent of Tmod1. However, myofibrils did not become striated, and gaps in F-actin staining (H zones) were never observed. We conclude that Tmod1 is required for regulation of actin filament lengths and myofibril maturation; this is critical for heart morphogenesis during embryonic development.

Ultrastructural Localization of Acid Mucosubstance in Skeletal Muscle

1967 ◽  
Vol 25 ◽  
pp. 52-53 ◽  
Author(s):  
William J. Dougherty ◽  
Samuel S. Spicer
Keyword(s):  
Striated Muscle ◽  
Divalent Cations ◽  
Ultrastructural Localization ◽  
Major Elements ◽  
Frozen Sections ◽  
Thorium Dioxide ◽  
Iron Solution ◽  
Coupling System ◽  
Psoas Muscles ◽  
Formalin Fixed

In recent years, considerable attention has focused on the morphological nature of the excitation-contraction coupling system of striated muscle. Since the study of Porter and Palade, it has become evident that the sarcoplastic reticulum (SR) and transverse tubules constitute the major elements of this system. The problem still exists, however, of determining the mechamisms by which the signal to interdigitate is presented to the thick and thin myofilaments. This problem appears to center on the movement of Ca++ions between myofilaments and SR. Recently, Philpott and Goldstein reported acid mucosubstance associated with the SR of fish branchial muscle using the colloidal thorium dioxide technique, and suggested that this material may serve to bind or release divalent cations such as Ca++. In the present study, Hale's iron solution adapted to electron microscopy was applied to formalin-fixed myofibrils isolated from glycerol-extracted rabbit psoas muscles and to frozen sections of formalin-fixed rat psoas muscles.

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 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.

scholarly journals Mg2+ Dependent Modulation of Striated Muscle Myosin ATPase by Thin Filament Components

2014 ◽  
Vol 106 (2) ◽  
pp. 769a
Author(s):  
Minae Kobayashi ◽  
Ben Ramirez
Keyword(s):  
Thin Filament ◽  
Striated Muscle ◽  
Myosin Atpase ◽  
Muscle Myosin
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