Figure 2.

Katanin severs Chlamydomonas axonemal microtubules. NP-40–permeabilized cells (≈1 × 10⁵ cells/ml) were incubated with purified katanin (100 μg/ml) plus 2.5 mM ADP (A) or 2.5 mM ATP (B–D) for 10 min. In the presence of ATP, katanin causes kinking (B), severing (C), and complete deflagellation (D) of individual flagella. (E and F) Katanin induces kinking and breakage of isolated flagellar axonemes. Flagella were excised from permeabilized wild-type cells by 1 × 10⁻⁶ M free Ca²⁺ and treated with either 5 mM ATP (E) or 5 mM ATP plus katanin (F) (100 μg/ml). As shown, the axonemes are fragmented only in the presence of both katanin and ATP.