Simulated cross-bridge patterns corresponding to ciliary beating in Paramecium

Abstract

It is generally accepted that bending of a cilium is caused by active sliding between outer doublets in the cilium produced by ATP-driven activation of their dynein–tubulin cross-bridges1–3. Changes with time in the location and extent of the active sliding regions in the outer doublets are thought to be primarily responsible for the changing shape of a beating cilium. However, using conventional techniques of biochemistry and electron microscopy, it is difficult to identify the regions on the outer doublets where active sliding occurs4. Here we have used computer simulation of the beating of a cilium to investigate changes in the distribution of activated cross-bridges, and hence of active sliding, in the nine outer doublets. Hereafter, the pattern of this distribution will be termed ‘cross-bridge pattern’. Published data have indicated that there is a periodically changing series of cross-bridge patterns in the nine outer doublets. On this assumption, the computer mimicked relatively well the beating of a cilium of Paramecium in media of both normal and high viscosity. The computer also simulated flagellar-type beating5, in which the cross-bridge patterns were modified slightly.