Electron microscopy and three-dimensional reconstruction of native thin filaments reveal species-specific differences in regulatory strand densities
Department of Cell Biology
Medical Subject Headings
Animals; Arachnida; Drosophila melanogaster; Microfilaments; Microscopy, Electron; Muscle, Skeletal; Rana pipiens; Species Specificity; Tropomyosin; Troponin T
Throughout the animal kingdom striated muscle contraction is regulated by the thin filament troponin-tropomyosin complex. Homologous regulatory components are shared among vertebrate and arthropod muscles; however, unique protein extensions and/or components characterize the latter. The Troponin T (TnT) isoforms of Drosophila indirect flight and tarantula femur muscle for example contain distinct C-terminal extensions and are approximately 20% larger overall than their vertebrate counterpart. Using electron microscopy and three-dimensional helical reconstruction of native Drosophila, tarantula and frog muscle thin filaments we have identified species-specific differences in tropomyosin regulatory strand densities. The strands on the arthropod thin filaments were significantly larger in diameter than those from vertebrates, although not significantly different from each other. These findings reflect differences in the regulatory troponin-tropomyosin complex, which are likely due to the larger TnT molecules aligning and extending along much of the tropomyosin strands' length. Such an arrangement potentially alters the physical properties of the regulatory strands and may help establish contractile characteristics unique to certain arthropod muscles.
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Citation: Biochem Biophys Res Commun. 2010 Jan 1;391(1):193-7. Epub 2009 Nov 10. Link to article on publisher's site