Electron Microscopic Recording of Myosin Head Power Stroke: Evidence That Myosin Heads Take the Neutral Position When Detached from Actin Filaments

2017 ◽  
pp. 113-137
Author(s):  
Haruo Sugi
Keyword(s):  
Actin Filaments ◽  
Myosin Head ◽  
Power Stroke ◽  
Neutral Position ◽  
Electron Microscopic

scholarly journals Electron microscopic recording of myosin head power stroke in hydrated myosin filaments

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Haruo Sugi ◽  
Shigeru Chaen ◽  
Tsuyoshi Akimoto ◽  
Hiroki Minoda ◽  
Takuya Miyakawa ◽  
...  
Keyword(s):  
Myosin Head ◽  
Power Stroke ◽  
Electron Microscopic ◽  
Myosin Filaments

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 Cytoskeletal reorganization of human platelets after stimulation revealed by the quick-freeze deep-etch technique.

1987 ◽  
Vol 105 (4) ◽  
pp. 1771-1780 ◽  
Author(s):  
T Nakata ◽  
N Hirokawa
Keyword(s):  
Actin Filaments ◽  
Plasma Membranes ◽  
Human Platelets ◽  
Electron Microscopic Level ◽  
Immunocytochemical Study ◽  
Cytoskeletal Reorganization ◽  
Electron Microscopic ◽  
Activated Platelets ◽  
Mixed Polarity ◽  
Cross Bridges

We studied the cytoskeletal reorganization of saponized human platelets after stimulation by using the quick-freeze deep-etch technique, and examined the localization of myosin in thrombin-treated platelets by immunocytochemistry at the electron microscopic level. In unstimulated saponized platelets we observed cross-bridges between: adjoining microtubules, adjoining actin filaments, microtubules and actin filaments, and actin filaments and plasma membranes. After activation with 1 U/ml thrombin for 3 min, massive arrays of actin filaments with mixed polarity were found in the cytoplasm. Two types of cross-bridges between actin filaments were observed: short cross-bridges (11 +/- 2 nm), just like those observed in the resting platelets, and longer ones (22 +/- 3 nm). Actin filaments were linked with the plasma membrane via fine short filaments and sometimes ended on the membrane. Actin filaments and microtubules frequently ran close to the membrane organelles. We also found that actin filaments were associated by end-on attachments with some organelles. Decoration with subfragment 1 of myosin revealed that all the actin filaments associated end-on with the membrane pointed away in their polarity. Immunocytochemical study revealed that myosin was present in the saponin-extracted cytoskeleton after activation and that myosin was localized on the filamentous network. The results suggest that myosin forms a gel with actin filaments in activated platelets. Close associations between actin filaments and organelles in activated platelets suggests that contraction of this actomyosin gel could bring about the observed centralization of organelles.

scholarly journals Biotinylphallotoxins: preparation and use as actin probes.

1989 ◽  
Vol 37 (7) ◽  
pp. 1035-1045 ◽  
Author(s):  
H Faulstich ◽  
S Zobeley ◽  
U Bentrup ◽  
B M Jockusch
Keyword(s):  
Actin Filaments ◽  
Ultrastructural Level ◽  
Microscopic Level ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Permeabilized Cells ◽  
High Affinity ◽  
Double Label ◽  
The One

We describe the synthesis of four phalloidin derivatives conjugated with biotin. An aminomethyldithiolane derivative of ketophalloidin was used as a reactive starter compound, and biotin residues were coupled to this molecule either directly, separated by spacer chains comprised of one or two glycyl residues, or of a 12-atom long chain constructed from succinic acid and hexamethylendiamine. Although all products still displayed a high affinity for F-actin, as seen in competition experiments with [3H]-demethylphalloidin, only the one with the longest spacer (BHPP) showed specific and high-affinity decoration of actin filaments in permeabilized cells, in conjunction with FITC-coupled avidin and fluorescence microscopy. Combined with gold-streptavidin, BHPP decorated the actin filament system at the light and electron microscopic level faithfully and with satisfactory density. Actin filaments polymerized in vitro from purified protein were not as densely labeled as had been expected. However, in all these experiments the new phalloidin probe, when combined with avidin or streptavidin, yielded clear and highly specific labeling of F-actin. Therefore, this system is useful to identify and localize actin unambiguously in microfilaments, independent of actin antibodies, and should facilitate double-label experiments on cytoskeletal components at the ultrastructural level.

scholarly journals X-ray Diffraction Studies on the Structural Origin of Dynamic Tension Recovery Following Ramp-Shaped Releases in High-Ca Rigor Muscle Fibers

2020 ◽  
Vol 21 (4) ◽  
pp. 1244
Author(s):  
Haruo Sugi ◽  
Maki Yamaguchi ◽  
Tetsuo Ohno ◽  
Hiroshi Okuyama ◽  
Naoto Yagi
Keyword(s):  
Muscle Contraction ◽  
Actin Filaments ◽  
Myosin Head ◽  
Muscle Fibers ◽  
Skinned Fibers ◽  
Myosin Filament ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tension Recovery ◽  
Pass Through

It is generally believed that during muscle contraction, myosin heads (M) extending from myosin filament attaches to actin filaments (A) to perform power stroke, associated with the reaction, A-M-ADP-Pi → A-M + ADP + Pi, so that myosin heads pass through the state of A-M, i.e., rigor A-M complex. We have, however, recently found that: (1) an antibody to myosin head, completely covering actin-binding sites in myosin head, has no effect on Ca2+-activated tension in skinned muscle fibers; (2) skinned fibers exhibit distinct tension recovery following ramp-shaped releases (amplitude, 0.5% of Lo; complete in 5 ms); and (3) EDTA, chelating Mg ions, eliminate the tension recovery in low-Ca rigor fibers but not in high-Ca rigor fibers. These results suggest that A-M-ADP myosin heads in high-Ca rigor fibers have dynamic properties to produce the tension recovery following ramp-shaped releases, and that myosin heads do not pass through rigor A-M complex configuration during muscle contraction. To obtain information about the structural changes in A-M-ADP myosin heads during the tension recovery, we performed X-ray diffraction studies on high-Ca rigor skinned fibers subjected to ramp-shaped releases. X-ray diffraction patterns of the fibers were recorded before and after application of ramp-shaped releases. The results obtained indicate that during the initial drop in rigor tension coincident with the applied release, rigor myosin heads take up applied displacement by tilting from oblique to perpendicular configuration to myofilaments, and after the release myosin heads appear to rotate around the helical structure of actin filaments to produce the tension recovery.

Calcium-dependent bidirectional power stroke of the dynein arms in sea urchin sperm axonemes

1996 ◽  
Vol 109 (12) ◽  
pp. 2833-2842 ◽  
Author(s):  
S. Ishijima ◽  
M. Kubo-Irie ◽  
H. Mohri ◽  
Y. Hamaguchi
Keyword(s):  
Light Microscopy ◽  
Sea Urchin ◽  
Electron Microscopic Examination ◽  
Dark Field ◽  
Power Stroke ◽  
Electron Microscopic ◽  
Calcium Dependent ◽  
Dynein Arms ◽  
Triton X ◽  
Sea Urchin Sperm

Active sliding between doublet microtubules of sea urchin sperm axonemes that were demembranated with Triton X-100 in the presence or absence of calcium was induced with ATP and elastase at various concentrations of Ca2+ to examine the effects of Ca2+ on the direction of the power stroke of the dynein arms. Dark-field light microscopy of microtubule sliding revealed that the sliding from the axonemes demembranated with Triton and millimolar calcium and disintegrated with ATP and elastase showed various patterns of sliding disintegration, including loops of doublet microtubules formed near the head or the basal body. These loops were often thicker than the remaining axonemal bundle. In contrast, only thinner loops were found from the axonemes demembranated with Triton in the absence of calcium and disintegrated with ATP and elastase at high Ca2+ concentrations. Electron microscopic examination of the direction of microtubule sliding showed that the doublet microtubules in the axonemes demembranated in the presence of millimolar calcium moved toward the base of the axonemes by the dynein arms on the adjacent doublet microtubule as well as by their own dynein arms. Doublet microtubules in the axonemes demembranated in the absence of calcium moved toward the base of the axonemes only by their own dynein arms. Similar observations have been obtained from the axonemes from which the outer dynein arms were selectively extracted. From these observations, we can conclude that the dynein arms generate force in both directions and this feature of the dynein arms arises from at least the inner dynein arms.

Electron microscopic images suggest both ends of caldesmon interact with actin filaments

1993 ◽  
Vol 14 (1) ◽  
pp. 54-64 ◽  
Author(s):  
Katsuhide Mabuchi ◽  
Jim J.-C. Lin ◽  
C.-L. Albert Wang
Keyword(s):  
Actin Filaments ◽  
Electron Microscopic ◽  
Microscopic Images
Sign in / Sign up

Export Citation Format

Share Document