Reactivation at low ATP distinguishes among classes of paralyzed flagella mutants

Abstract

Paralyzed flagella (pf) mutants of Chlamydomonas have been distinguished by the inability of the intact cells to move. Demembranated flagella from these mutants are also immotile when reactivated under standard conditions, with millimolar ATP concentrations. Three of these pf mutants were previously found to be motile when reactivated under 3 alternate reactivation conditions: low ATP concentration (< or =50 microM); 0.1 mM ATP combined with >0.5 mM ADP; or 0.1 mM ATP combined with non-reactivating ATP analogs anthraniloyl ATP or methylanthraniloyl ATP. We have now surveyed all pf mutants in the Chlamydomonas Culture Collection and discovered that a great majority of these mutants can move under these alternate nucleotide conditions. Only pf22 and pf23, mutants missing multiple subsets of dynein arms, did not reactivate under those conditions. This suggests that the paralysis observed in most pf mutants is the result of inhibition by physiological ATP. Except for pf12, which has an abnormally symmetric bending pattern, all other pf mutants exhibit asymmetric bending patterns similar to wild-type. Previously, motility that was restored by the presence of suppressor mutations was found to lack the normal asymmetry of wild-type flagella or the suppressor by itself. The waveform of pf mutants at alternate reactivation conditions in the absence of suppressor shows that pf mutants with radial-spoke or central-pair defects are capable of asymmetric bending similar to wild-type. A complete radial-spoke/central-pair complex is not essential for the production of asymmetric bending patterns. Furthermore, this suggests that the symmetric waveform observed previously in suppressed pf mutants is due to the interaction between the pf and suppressor mutations.