Oiwa K, Takahashi K
Zoological Institute, Faculty of Science, University of Tokyo, Japan.
Cell Struct Funct. 1988 Jun;13(3):193-205. doi: 10.1247/csf.13.193.
We studied the relationship between the force and velocity of microtubule sliding in demembranated sperm flagella of the sea urchin, Hemicentrotus pulcherrimus, under auxotonic conditions following a quick release of the tension between sliding microtubules. The shape of the force-velocity curve was independent of the concentration of Mg-ATP over the range of 3.7 to 350 microM and appeared either linear or was the reverse of the hyperbolic curve seen for muscle. The power, calculated as the product of velocity and force, passed through a peak at c. 0.7 Fmax (the maximal isometric force). Thus, the maximal power is attained at a larger relative load than in muscle. The sliding velocity at 0.1 Fmax showed a hyperbolic dependence on Mg-ATP concentration, with a Km of 210 microM and a Vmax of 19 micron.sec-1. The maximal force did not significantly change over the Mg-ATP concentration range of 3.7 to 350 microM. These results are discussed in terms of a crossbridge model similar to the one originally proposed by Huxley. It is suggested that the dynein crossbridge cycle is characterized by a relatively rapid rate of attachment and a relatively slow rate of detachment.
我们研究了在海胆（Hemicentrotus pulcherrimus）去膜精子鞭毛中微管滑动的力与速度之间的关系，实验条件为在快速释放滑动微管之间的张力后进行辅助等张条件下的实验。在3.7至350微摩尔范围内，力-速度曲线的形状与Mg-ATP浓度无关，呈现出线性或与肌肉中所见的双曲线相反的形状。功率计算为速度与力的乘积，在约0.7 Fmax（最大等长力）处达到峰值。因此，与肌肉相比，在更大的相对负荷下可达到最大功率。在0.1 Fmax时的滑动速度对Mg-ATP浓度呈现双曲线依赖性，Km为210微摩尔，Vmax为19微米·秒⁻¹。在3.7至350微摩尔的Mg-ATP浓度范围内，最大力没有显著变化。我们根据类似于赫胥黎最初提出的那种横桥模型来讨论这些结果。有人提出，动力蛋白横桥循环的特点是附着速率相对较快，而脱离速率相对较慢。
