CONTRACTION OF RABBIT SKINNED SKELETAL-MUSCLE FIBERS AT LOW-LEVELS OF MAGNESIUM ADENOSINE-TRIPHOSPHATE
CONTRACTION OF RABBIT SKINNED SKELETAL-MUSCLE FIBERS AT LOW-LEVELS OF MAGNESIUM ADENOSINE-TRIPHOSPHATE
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DOI：
10.1016/s0006-3495(84)84216-2
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发表时间：
1984-01-01
影响因子：
3.4
通讯作者：
HAWORTH, RA
中科院分区：
文献类型：
--
作者：
MOSS, RL;HAWORTH, RA
在低MgATP和无Ca2+（即< 10-8 M）条件下，研究了兔腰肌剥皮单纤维的收缩特性。1。M MgATP，纤维在最大速度为660 .+-时缩短。420 .ANG。/半肌节/ s (n = 9)，而3.4万。在1mm MgATP下最大Ca2+激活时测量的/半肌节/s。观察到Vmax在7.0和5.3之间对pMgATP的依赖性与Weber， A， R. Herz和I. Reiss先前测量的肌动球蛋白atp酶相似。等长张力与pMgATP的变化方式很像Reuben， J.P， P.W. Brandt， M. Berman和H. Grundfest所报道的。建立了一个简单的跨桥模型来模拟高、低水平MgATP的收缩行为。如果使桥架的脱离速率与MgATP的浓度成正比，则Vmax和ATPase对pMgATP的依赖性可以成功地建模。在该模型中，Vmax和ATP酶对pMgATP的相似依赖性来源于这样一个事实，即在pMgATP的这个范围内，肌动蛋白位点的每一次过桥都会导致一个附着-分离循环，而每个这样的循环都会导致1分子ATP的水解。
The contractile properties of skinned single fibers from rabbit psoas muscle were investigated under conditions of low MgATP and no Ca2+ (i.e., < 10-8 M). At 1 .mu.M MgATP, fibers shortened at a maximum velocity of 660 .+-. 420 .ANG./half sarcomere per s (n = 9), compared with 34,000 .ANG./half sarcomere/s measured during maximum Ca2+-activation at 1 mM MgATP. The observed dependence of Vmax on pMgATP between 7.0 and 5.3 was similar to that of actomyosin ATPase measured previously by Weber, A., R. Herz, and I. Reiss. Isometric tension was found to vary with pMgATP in a manner much like that reported by Reuben, J.P., P.W. Brandt, M. Berman, and H. Grundfest. A simple cross-bridge model was developed to simulate contractile behavior at both high and low levels of MgATP. The pMgATP dependence of Vmax and ATPase could be successfully modeled if the rate of detachment of the cross-bridge was made proportional to the concentration of MgATP. In the model, the similar dependence of Vmax and ATPase on pMgATP was derived from the fact that in this range of pMgATP every pass of a cross-bridge by an actin site resulted in an attachment-detachment cycle, and every such cycle caused hydrolysis of 1 molecule of ATP.