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Three-dimensional reconstruction of ...
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Cammarato, Anthony Ross.
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Three-dimensional reconstruction of insect flight muscle thin filaments.
Record Type:
Electronic resources : Monograph/item
Title/Author:
Three-dimensional reconstruction of insect flight muscle thin filaments./
Author:
Cammarato, Anthony Ross.
Description:
155 p.
Notes:
Source: Dissertation Abstracts International, Volume: 64-05, Section: B, page: 1968.
Contained By:
Dissertation Abstracts International64-05B.
Subject:
Biology, Animal Physiology. -
Online resource:
http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3090399
Three-dimensional reconstruction of insect flight muscle thin filaments.
Cammarato, Anthony Ross.
Three-dimensional reconstruction of insect flight muscle thin filaments.
- 155 p.
Source: Dissertation Abstracts International, Volume: 64-05, Section: B, page: 1968.
Thesis (Ph.D.)--Boston University, 2004.
A "steric blocking model" of thin filament (TF) regulation in which tropomyosin (TM) strands interfere with myosin crossbridge binding was investigated in the indirect flight muscle (IFM) of Drosophila by electron microscopy (EM) and 3-D reconstruction. In this model TM is thought to block contraction in the absence of Ca2+ and move in the presence of Ca2+ to expose myosin binding sites. In the present study TFs, isolated directly from mutant myosin-less ( Mhc7) Drosophila IFM, were negatively stained, and EM images showed actin strands with tropomyosin and periodically arranged troponin complexes. Helical image reconstructions that delineated TM positions on IFM actin in the absence and presence of Ca2+ were indistinguishable from those reported for vertebrate striated muscle thin filaments. Results support the steric blocking model already described in vertebrates. In an initial attempt to examine the influence of regulatory protein alterations on the steric blocking mechanism, IFM TFs from the Drosophila mutant heldup2 ( hdp2), which possesses a single amino acid conversion in Troponin I, were also analyzed structurally. The position of TM on the hdp2 TFs in both the Ca2+-free and Ca2+-induced states was the same, and equivalent to that of wild-type IFM TFs in the presence of Ca2+. In these muscles the exposed myosin binding sites would allow crossbridge cycling to proceed uninhibited and thus account for the hyper-contraction characteristic of IFM fibers in the mutants. The ability to evaluate TM positions on mutant IFM thin filaments provides an in vivo model system to probe the effects of other TF protein variants, including those that mimic myopathies in higher organisms, and relate these to steric regulation. The thin filament regulatory proteins expressed in arthropods differ from those of vertebrates. Hence, a structural comparison of thin filaments from these phyla was carried out. TM strands on TFs of the arthropods, Drosophila and tarantula, were significantly larger in diameter than those from vertebrates, although they were not noticeably different from each other. These findings are likely to reflect known phylogenetic differences in regulatory protein components and/or their organization on thin filaments.Subjects--Topical Terms:
1017835
Biology, Animal Physiology.
Three-dimensional reconstruction of insect flight muscle thin filaments.
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A "steric blocking model" of thin filament (TF) regulation in which tropomyosin (TM) strands interfere with myosin crossbridge binding was investigated in the indirect flight muscle (IFM) of Drosophila by electron microscopy (EM) and 3-D reconstruction. In this model TM is thought to block contraction in the absence of Ca2+ and move in the presence of Ca2+ to expose myosin binding sites. In the present study TFs, isolated directly from mutant myosin-less ( Mhc7) Drosophila IFM, were negatively stained, and EM images showed actin strands with tropomyosin and periodically arranged troponin complexes. Helical image reconstructions that delineated TM positions on IFM actin in the absence and presence of Ca2+ were indistinguishable from those reported for vertebrate striated muscle thin filaments. Results support the steric blocking model already described in vertebrates. In an initial attempt to examine the influence of regulatory protein alterations on the steric blocking mechanism, IFM TFs from the Drosophila mutant heldup2 ( hdp2), which possesses a single amino acid conversion in Troponin I, were also analyzed structurally. The position of TM on the hdp2 TFs in both the Ca2+-free and Ca2+-induced states was the same, and equivalent to that of wild-type IFM TFs in the presence of Ca2+. In these muscles the exposed myosin binding sites would allow crossbridge cycling to proceed uninhibited and thus account for the hyper-contraction characteristic of IFM fibers in the mutants. The ability to evaluate TM positions on mutant IFM thin filaments provides an in vivo model system to probe the effects of other TF protein variants, including those that mimic myopathies in higher organisms, and relate these to steric regulation. The thin filament regulatory proteins expressed in arthropods differ from those of vertebrates. Hence, a structural comparison of thin filaments from these phyla was carried out. TM strands on TFs of the arthropods, Drosophila and tarantula, were significantly larger in diameter than those from vertebrates, although they were not noticeably different from each other. These findings are likely to reflect known phylogenetic differences in regulatory protein components and/or their organization on thin filaments.
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http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3090399
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