Yi. Fang et al., PUREALIN BLOCKS THE SLIDING MOVEMENT OF SEA-URCHIN FLAGELLAR AXONEMESBY SELECTIVE-INHIBITION OF HALF THE ATPASE ACTIVITY OF AXONEMAL DYNEINS, Biochemistry, 36(50), 1997, pp. 15561-15567
Ciliary and flagellar movements are explained by active sliding betwee
n the outer doublet microtubules of an axoneme via their inner and out
er dynein arms. Purealin, a novel bioactive principle of a sea sponge
Psammaplysilla purea, blocked the motility of Triton-demembranated sea
urchin sperm flagella within 5 min at concentrations above 20 mu M. I
n a similar concentration range, purealin blocked the sliding movement
of the flagellar axonemes in vitro within a few minutes judging from
the turbidity measurements. The ATPase activity of axonemes was partia
lly inhibited by purealin in a concentration-dependent manner. The max
imum inhibition reached approximately 50% at concentrations above 20 m
u M, indicating that half the axonemal ATPase activity is sensitive to
purealin. Similar results were observed on the ATPase activity of out
er-arm-depleted axonemes and that of a mixture of 21S dynein and salt-
extracted axonemes. On the other hand, ATPase activity of isolated 21S
dynein was not inhibited by purealin. The inhibitory action of pureal
in on the axonemal ATPases was reversed by dilution of purealin. The e
ffect of purealin on the double-reciprocal plot of the ATPase activity
as a function of ATP concentrations showed that the inhibition was no
t a competitive type. In accord with this finding, purealin did not af
fect the vanadate-mediated UV photocleavage of axonemal dyneins. These
results suggest that purealin binds reversibly to a site other than t
he catalytic ATP-binding site and inhibits half the ATPase activity of
axonemes. Taken together, our results suggest that purealin-sensitive
ATPase activity of the dynein arms plays an essential role in generat
ing the sliding movement of flagellar axonemes.