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STEM Analysis of Caenorhabditis elegans muscle thick filaments: evidence for microdifferentiated substructuresIn the thick filaments of body muscle in Caenorhabditis elegans, myosin A and myosin B isoforms and a subpopulation of paramyosin, a homologue of myosin heavy chain rods, are organized about a tubular core. As determined by scanning transmission electron microscopy, the thick filaments show a continuous decrease in mass-per-length (MPL) from their central zones to their polar regions. This is consistent with previously reported morphological studies and suggests that both their content and structural organization are microdifferentiated as a function of position. The cores are composed of a second distinct subpopulation of paramyosin in association with the alpha, beta, and gamma-filagenins. MPL measurements suggest that cores are formed from seven subfilaments containing four strands of paramyosin molecules, rather than the two originally proposed. The periodic locations of the filagenins within different regions and the presence of a central zone where myosin A is located, implies that the cores are also microdifferentiated with respect to molecular content and structure. This differentiation may result from a novel "induced strain" assembly mechanism based upon the interaction of the filagenins, paramyosin and myosin A. The cores may then serve as "differentiated templates" for the assembly of myosin B and paramyosin in the tapering, microdifferentiated polar regions of the thick filaments.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Muller, S. A.
(Maurice E. Muller Institute Biozentrum, University of Basel CH-4056 Basel, Switzerland)
Haner, M.
Ortiz, I.
Aebi, U.
Epstein, H. F.
Date Acquired
August 21, 2013
Publication Date
February 2, 2001
Publication Information
Publication: Journal of molecular biology
Volume: 305
Issue: 5
ISSN: 0022-2836
Subject Category
Life Sciences (General)
Distribution Limits
NASA Discipline Musculoskeletal
Non-NASA Center

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