| It has been demonstrated previously that actin in the dormant spores of Dictyostelium discoideum can be dephosphorylated when incubated in glucose solutions. The work reported here supports and extends previous work demonstrating that actin as well as a 66 kilodalton (kDa) protein were dephosphorylated when dormant spores of Dictyostelium were incubated in a glucose of 100 mM for 1 hour. The dephosphorylation of both of these proteins was inhibited by hydrogen peroxide. Furthermore, the addition of the reducing agent, dithiothreitol (DTT), along with glucose and hydrogen peroxide (H2O2), allowed for the dephosphorylation of actin but not the 66 kDa protein. It also was observed in vitro that the cysteine proteases of Dictyostelium could be inhibited by hydrogen peroxide and that enzyme activity could be restored by the addition of the reducing agent DTT. It was demonstrated here that the previously characterized nonacid activatable cysteine protease CP18 found in the spore matrix was acid activatable when sodium dodecyl sulfate (SDS) was absent from the polyacrylamide gel electrophoresis system (PAGE). However, the cysteine proteases of Dictyostelium were found to have no direct involvement anywhere in the life cycle. (Abstract shortened by UMI.)... |
