A rho gene product in human blood platelets. II. Effects of the ADP-ribosylation by botulinum C3 ADP-ribosyltransferase on platelet aggregation.

In the accompanying paper (Nemoto, Y., Namba, T., Teru-uchi, T.

A rho gene product in human blood platelets. I. Identification of the platelet substrate for botulinum C3 ADP-ribosyltransferase as rhoA protein.

A substrate protein for botulinum C3 ADP-ribosyltransferase (C3 exoenzyme) in human platelets was purified to apparent homogeneity from the cytosol by ammonium sulfate fractionation and successive chromatography on columns of DEAE-Sepharose, hydroxylapatite, phenyl-Sepharose, and TSK phenyl-5PW. The purified protein yielded an amino acid sequence identical to that of rhoA protein. When platelet cytosol and membranes were incubated with C3 exoenzyme and [32P]NAD and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing, they gave only one [32P]ADP-ribosylated band on each electrophoresis that showed an M(r) of 22,000 and a pI of 6.