Inhibition of cytochalasin D-stimulated G-actin ATPase by ADP-ribosylation with Clostridium perfringens iota toxin

Abstract

Clostridium perfringens iota toxin belongs to a novel family of actin-ADP-ribosylating toxins. The effects of ADP-ribosylation of skeletal muscle actin by Clostridium perfringens iota toxin on cytochalasin D-stimulated actin ATPase activity was studied. Cytochalasin D stimulated actin-catalysed ATP hydrolysis maximally by about 30-fold. ADP-ribosylation of actin completely inhibited cytochalasin D-stimulated ATP hydrolysis. Inhibition of ATPase activity occurred at actin concentrations below the critical concentration (0.1 microM), at low concentrations of Mg2+ (50 microM) and even in the actin-DNAase I complex, indicating that ADP-ribosylation of actin blocks the ATPase activity of monomeric actin and that the inhibitory effect is not due to inhibition of the polymerization of actin.

Clostridial ADP-ribosyltransferases ? Modification of low molecular weight GTP-binding proteins and of actin by clostridial toxins

“…Actin-associated ATPase activity is increased concomitantly with polymerization. The ADP-ribosylation inhibits the ATP hydrolysis catalyzed by actin (Geipel et al , 1990). Various findings indicate that the inhibitory effect on ATP hydrolysis is not simply due to inhibition of actin polymerization but is caused by inhibition of G-actin ATPase: firstly, inhibition of ATPase by ADPribosylation is observed at low Mg 2+ (50 laM) concentrations, which are apparently too low to induced polymerization.…”

ADP-ribosylation of actin

“…ADPribosylation of actin inhibits the ATP hydrolysis catalyzed by actin . This inhibitory effect is observed with G-actin below its critical concentration and with cytochalasin-stimulated G-actin ATPase indicating that inhibition of ATP hydrolysis is not simply due to the blockade of actin polymerization (Geipel et al, 1990). ADP-ribosylation of actin by the toxins is reversible at high concentrations of nicotinamide (30 mM) and results in the reconstitution of actin properties, such as an increase in actin ATPase activity .…”

Binary Bacterial Toxins: Biochemistry, Biology, and Applications of CommonClostridiumandBacillusProteins

“…An actin-gelsolin complex, in which gelsolin facilitates actin nucleation and subsequent polymerization, is also modified by as well as C2 toxins that block additional nucleation activity (30,201,462,476). Additionally, the and C2 toxins ADP-ribosylate G-actin complexed with ATPase, which results in an increased exchange, but decreased hydrolysis, of ATP (145,146). From the perspective of bacterial survival, disruption of a eukaryotic cytoskeleton and reduction of ATP hydrolysis can prevent phagocytosis (16), intracellular trafficking, and ultimately induce cell death with subsequent release of valuable nutrients.…”