Effects of p-Chloromercuriphenylsulfonate on Ciliary Dynein Adenosine Triphosphatase Activity of Tetrahymena pyriformis

Abstract

Ciliary dynein of Tetrahymena pyriformis was investigated in relation to the susceptibility of the ATPase activity [EC 3.6.1.31 to p-chloromercuriphenylsulfonate (PCMPS). Like N-ethylmaleimide (NEM), PCMPS caused a biphasic alteration of 30S dynein ATPase activity and inhibition only of 14S dynein ATPase activity. However, the magnitude of the activation of 30S dynein was smaller than that induced by NEM, that is, 55–65 % for Mg-ATPase and 30–75% for Ca-ATPase. The concentrations of PCMPS required for maximal activation of 30S dynein were 4–8 μM (2.7–5.4 mol/10⁵ g protein) for Mg-ATPase and 2–4 μM for Ca-ATPase, which were significantly lower than those of NEM. Upon subsequent addition of dithiothreitol (DTT), though the enzyme activity of modified 14S dynein was recovered to a large extent, the recovery of PCMPS-treated 30S dynein ATPase activity depended upon the conditions under which 30S dynein was preincubated. In general, however, the inhibition caused by high concentrations of PCMPS was removed, but the PCMPS-induced increase in the activity remained to some extent. These effects of PCMPS on 30S dynein were affected by the presence of ATP in the preincubation medium. The PCMPS-induced enhancement of the enzyme activity was considerably repressed, accompanied by more marked inhibition at higher concentrations of PCMPS. Recovery of the enzyme activity after addition of DTT was smaller in the presence of ATP than in its absence. 30S Dynein fully activated by PCMPS was only inhibited by another treatment with NEM and vice versa, showing that the effects of the two SH-blocking reagents are not additive but may well be identical.