Submicrosecond and microsecond rotational motions of myosin head in solution and in myosin synthetic filaments as revealed by time-resolved optical anisotropy decay measurements
Submicrosecond and microsecond rotational motions of myosin head in solution and in myosin synthetic filaments as revealed by time-resolved optical anisotropy decay measurements
复制标题
时间分辨光学各向异性衰减测量揭示了溶液中和肌球蛋白合成丝中肌球蛋白头的亚微秒和微秒旋转运动
DOI：
10.1021/bi00320a012
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发表时间：
1984
期刊：
影响因子：
2.9
通讯作者：
A. Ikegami
中科院分区：
文献类型：
--
作者：
K. Kinosita;S. Ishiwata;H. Yoshimura;H. Asai;A. Ikegami
Kazuhiko Kinosita, Jr., Shin’ichi Ishiwata,* Hideyuki Yoshimura, 1 Hiroshi Asai, and Akira Ikegami abstract: Rotational Brownian motions of the head portion (subfragment 1) of rabbit skeletal myosin were studied by the measurement of flash-induced absorption anisotropy decay and phosphorescence anisotropy decay of the triplet probe 5-eo-sinylmaleimide bound to the myosinhead. Fluorescence an-isotropy decay of the fluorescent probe A-(1-pyrenyljmaleimide was also examinedin some cases. Most of the triplet signals were observed in the presence of 60%(w/w) sucrose, which simply reduced the rate of motion via viscosity damping, to obtain good time resolution. Anisotropy decay of eosin on isolated head fragment was single exponential over two dec-ades; the data indicated that the largest diameter of the head was 14-17 nm if the head was modeled as a prolate ellipsoid of revolution and 12-13 nm if oblate. Anisotropy decay in myosin synthetic filaments consisted of a fast and a slow component and a small constant part; myosin monomers and heavy meromyosin gave similar but somewhat faster decays with a smaller residual anisotropy. For each sample, the decay curves between-10 and 30 C overlapped with each other after reducing the time scale to that at 20 C in the absence of sucrose, showing that no gross conformational changes oc-curred between these temperatures. The fast decay was in the submicrosecond range on the reduced time scale andcould be explained by a wobbling motion of the head around the head-rod junction within a cone of semiangle 35 for filament and 41 for solubilizedproteins. The slow decay had a re-laxation time of a few microseconds and indicatedthat a part of the rod portion next to thehead also wobbled extensively. Analysis in which the rodend was assumed to wobbleuni-formly in a cone suggested that the effective length of the wobbling part was about 14 nm, and the cone angle was es-timated to be about 48 in filament and 57-60 for solubilized proteins. e molecular mechanism of muscle contraction is not yet fully understood. In striated muscles of vertebrates, sliding motion of the thick and thin filaments past each other leads to contraction (Huxley & Niedergerke, 1954; Huxley & Hanson, 1954), although shortening of the filaments them-selves might also take place undercertain conditions [see review by Pollack (1983)]. During contraction, the cross bridges projectingfrom the thick (myosin) filament approach the thin (actin) filaments; the force pulling the two sets of filaments against each other is apparently mediated by the cross bridges (Huxley, 1969). Where and how the force is generated, however, are still challenging problems.
肌原纤维中自旋标记的肌球蛋白头的亚毫秒旋转动力学。
影响因子：
3.4
作者：
Thomas,DD;Ishiwata,S;Seidel,JC;Gergely,J
通讯作者：
Gergely,J