Reverse motion of organelles with myosin molecules along bundles of the actin filaments in a Characean internodal cell

We have visualized bundles of the actin filaments of a Characean internodal cell and investigated the sliding motion of organelles with myosin an the bundles. The investigation revealed that a power spectrum of the sliding ve locity time series of the organelle has two remarkable peaks near 4 and 7.5 Hz. This suggests that myosin molecules attached to the organelle not inde pendently but cooperatively produce the sliding force. Moreover, we have fo und that some organelles move in the opposite direction of their sliding mo tion for several hundred milliseconds along the bundles. The fluctuation an alysis of that motion showed that a power spectrum profile of the reverse v elocity time series almost agreed with that of the sliding velocity time se ries. This result suggests that the dynamics of the reverse motion is the s ame as that of the sliding motion. (C) 1999 Academic Press.