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Cryo-Electron Tomography of Isolated Triad Junctions from Skeletal Muscle

Published online by Cambridge University Press:  02 July 2020

C.-E. Hsieh ,
M. Marko ,
B.K. Rath ,
S. Fleischer  and
T. Wagenknecht
C.-E. Hsieh
Affiliation:
Resource for Visualization of Biological Complexity, Wadsworth Center, Empire State Plaza, Albany, NY, 12201-0509
M. Marko
Affiliation:
Resource for Visualization of Biological Complexity, Wadsworth Center, Empire State Plaza, Albany, NY, 12201-0509
B.K. Rath
Affiliation:
Resource for Visualization of Biological Complexity, Wadsworth Center, Empire State Plaza, Albany, NY, 12201-0509
S. Fleischer
Affiliation:
Dept. of Biological Sciences, Vanderbilt University, Nashville, TN, 37232
T. Wagenknecht
Affiliation:
Resource for Visualization of Biological Complexity, Wadsworth Center, Empire State Plaza, Albany, NY, 12201-0509
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Abstract

In skeletal muscle, depolarization of the plasma membrane, which is initiated at the neuromuscular junction, is transduced to a rise in cytoplasmic calcium at specialized structures known as triad junctions (TJs). TJs occur in the myofiber’s interior at regions near the z-lines, where transversely oriented tubular invaginations of the plasma membrane (T-tubules) form junctions with two elements of the sarcoplasmic reticulum (SR). Isolation of membrane fractions that are enriched in junctional complexes and which retain function has been reported.

Figure 1 shows a region of an electron micrograph containing an isolated TJ in the frozen-hydrated state. in the orientation shown, two SR-derived vesicles sandwich a flattened vesicle derived from the T-tubule. The junctional regions contain a complex distribution of density, presumably due to proteins that are known to be present in TJs. Electron tomography offers the means to determine the three-dimensional mass density from such micrographs, which would greatly aid in their interpretation. Only recently has the automated data collection technology for determining tomograms of non-stained, frozen-hydrated specimens become available. Here we describe the first tomographic reconstruction of a frozen-hydrated triad junction by automated electron tomography.

Type
Electron Tomography: Recent Advances and Applications (Organized by M. Marko)
Information
Microscopy and Microanalysis , Volume 7 , Issue S2: Proceedings: Microscopy & Microanalysis 2001, Microscopy Society of America 59th Annual Meeting, Microbeam Analysis Society 35th Annual Meeting, Long Beach, California August 5-9, 2001 , August 2001 , pp. 94 - 95
Copyright
Copyright © Microscopy Society of America 2001

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References

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