Abstract
Glycerol‐extracted cilia from Tetrahymena pyriformis were demembranated by treatment with Triton X‐100 and then heated for up to 30 min at temperatures between 34–38°C. Heat treatment carsed an uncoupling of the ATPase from motility as indicated by an increase in ATPase activity and a loss of pellet height response. After heat treatment, the ATPase activity of the dynein in situ differed from that in unheated cilia as shown by an increased sensitivity to a lower temperature of assay (0°C) and by a loss of the activation normally observed upon reaction with N‐ethylmaleimide or p‐phenylenedimaleimide. Upon extraction of the heat‐treated cilia by Tris‐EDTA, there was a large loss in ATPase activity so that the heat‐treated cilia yielded a crude dynein fraction with a lower specific activity compared with that obtained from unheated controls. The difference was not due to a change in the amount of protein recovered or in the amount of ATPase activity which remained unextracted. Resolution of the crude dynein by sucrose density sedimentation indicated that activity was lost from both the 14S and 30S peaks but more so from the latter than from the former. Thus dynein in situ in cilia in which the ATPase has been uncoupled from motility by gentle heat treatment differs in several important respects from dynein inside unheated cilia.