Structural changes in the thin filament during activation studied by X-ray diffraction of highly stretched skeletal muscle.
The actin layer-lines were recorded from a frog semitendinosus muscle stretched to a sarcomere length greater than 4.4 microM. On activation of the muscle, the equator, the second layer-line at 1/18 nm-1 and the 5.9 nm layer-line increased in integrated intensity. On the other hand, the integrated intensity of the first layer-line at 1/36 nm-1 decreased markedly on activation. This decrease was not fully attributable to shifts of tropomyosin strands and therefore suggested a structural change in the actin subunit. The decrease may account for the apparent lack of an intensity increase of this layer-line on activation at normal muscle lengths where attachment of myosin heads to actin increases the intensities of other layer-lines.
Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan.
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N
Yagi
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Matsubara
D000199:Actins; D000818:Animals; D008954:Models, Biological; D009132:Muscles / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D014335:Tropomyosin / Q000378:metabolism; D014961:X-Ray Diffraction
D000199:Actins; D014335:Tropomyosin; D009218:Myosins