Fig. 1. (A,B) Elastase-treated axonemes before (left) and after (right) ATP application. 20 µM ATP at <10^–9 M Ca²⁺ induced more than two sliding events, causing sliding disintegration of axonemes into individual doublets (A), whereas 1 mM ATP at 10^–4 M Ca²⁺ induced one sliding event that caused splitting of the axoneme into a pair of doublet bundles (B). The thinner bundle slid over the thicker bundle to the left (arrow in B). (C) Proportions of three types of sliding, categorized by the total number of sliding events (1, 2 and 3). Left, <10^–9 M Ca²⁺, 20 µM ATP; middle, <10^–9 M Ca²⁺, 1 mM ATP; right, 10^–4 M Ca²⁺, 1 mM ATP.