ADP-ribosylation of gelsolin-actin complexes by clostridial toxins.
ADP-ribosylation of the 1:1 (G-A) and 1:2 (G-A-A) gelsolin-actin complexes by Clostridium perfringens iota toxin and Clostridium botulinum C2 toxin was studied. Iota toxin ADP-ribosylated actin in the G-A complex from human platelets as effectively as skeletal muscle actin. The Km for NAD (4 microM) was identical for both substrates. C2 toxin ADP-ribosylated actin in the G-A complex with lower efficacy than nonmuscle actin from platelet cytosol. In the G-A-A complex both actin molecules were ADP-ribosylated by iota toxin. The G-A complex bound ADP-ribosylated actin (Ar) to form the G-A-Ar complex in which the weakly bound actin is ADP-ribosylated. Vice versa, ADP-ribosylated 1:1 gelsolin-actin complex (G-Ar) was able to bind unmodified actin to yield the G-Ar-A complex. ADP-ribosylation did not change the nucleation activity of either the G-Ar complex or the G-Ar-A complex. When monomeric actin was added to the G-A-Ar complex, polymerization of actin was delayed by about 10 min. According to a quantitative kinetic analysis, the delay of polymerization corresponded to the rate of dissociation of ADP-ribosylated actin from the G-A-Ar complex. This suggests that the nucleation activity of the G-A-A complex is inhibited by ADP-ribosylation of the weakly bound actin and that the inhibition can be removed by dissociation of ADP-ribosylated actin from the G-A-Ar complex.
Wille
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Rudolf-Buchheim-Institut für Pharmakologie der Universität Giessen, Germany.
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Wegner
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D036002:ADP Ribose Transferases; D000199:Actins / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western; D001905:Botulinum Toxins / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003016:Clostridium perfringens / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D018260:Gelsolin; D006801:Humans; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D011817:Rabbits; D013379:Substrate Specificity
D000199:Actins; D001427:Bacterial Toxins; D002135:Calcium-Binding Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; C050737:iota toxin, Clostridium perfringens; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; D001905:Botulinum Toxins