Minoura I, Kamiya R
Zoological Institute, Graduate School of Science, University of Tokyo, Japan.
Cell Motil Cytoskeleton. 1995;31(2):130-9. doi: 10.1002/cm.970310205.
The propulsive force generated by Chlamydomonas mutants deficient in flagellar dynein was estimated from their swimming velocities in viscous media. The force produced by wild-type cells increased by 30-40% when viscosity was raised from 0.9 to 2 cP but decreased as viscosity was further raised above 6 cP. The biphasic dependence of force generation on viscosity was also observed in the mutant ida1, which lacks the I1 component of the inner-arm dynein. The mutant ida4, which lacks the inner-arm I2 component, was extremely susceptible to viscosity and stopped swimming at 6 cP, at which other mutants could swim. In contrast, oda1, which lacks the entire dynein outer arm, produced a fairly constant force of about one-third of the wild-type value, over a viscosity range of 0.9-11 cP. In demembranated and reactivated cell models of the wild type, the propulsive force decreased monotonically as viscosity increased. Thus the increase in force generation at about 2 cP observed in live cells may be caused by some unknown mechanism that is lost in cell models. The cell models of oda1, in contrast, did not show a marked change in force generation with the change in viscosity. These results indicate that the force generation by the outer-arm dynein greatly depends on viscosity or the velocity of movement, whereas the complete set of inner-arm dynein present in the oda1 axoneme produces a fairly constant force at different viscosities. These different properties of inner and outer dynein arms should be important in the mechanism that produces flagellar beating.
通过缺乏鞭毛动力蛋白的衣藻突变体的游动速度，估算出其产生的推进力。当粘度从0.9厘泊提高到2厘泊时，野生型细胞产生的力增加了30%-40%，但当粘度进一步提高到6厘泊以上时，力则下降。在缺乏内臂动力蛋白I1成分的突变体ida1中，也观察到了力产生对粘度的双相依赖性。缺乏内臂I2成分的突变体ida4对粘度极为敏感，在6厘泊时停止游动，而其他突变体在该粘度下仍能游动。相比之下，缺乏整个动力蛋白外臂的oda1在0.9-11厘泊的粘度范围内产生的力相当恒定，约为野生型值的三分之一。在野生型的去膜并重新激活的细胞模型中，推进力随粘度增加而单调下降。因此，活细胞中在约2厘泊时观察到的力产生增加可能是由细胞模型中丧失的某种未知机制引起的。相比之下，oda1的细胞模型在粘度变化时力的产生没有明显变化。这些结果表明，外臂动力蛋白产生的力极大地依赖于粘度或运动速度，而oda1轴丝中存在的完整内臂动力蛋白在不同粘度下产生相当恒定的力。内、外动力蛋白臂的这些不同特性在产生鞭毛摆动的机制中应该很重要。
