REVERSIBLE ADP-RIBOSYLATION AS A MECHANISM OF ENZYME REGULATION IN PROKARYOTES

Several cases of ADP-ribosylation of endogenous proteins in procaryote s have been discovered and investigated. The most thoroughly studied e xample is the reversible ADP-ribosylation of the dinitrogenase reducta se from the photosynthetic bacterium Rhodospirillum rubrum and related bacteria. A dinitrogenase reductase ADP-ribosyltransferase (DRAT) and a dinitrogenase reductase ADP-ribose glycohydrolase (DRAG) from R. ru brum have been isolated and characterized. The genes for these protein s have been isolated and sequences and show little similarity to the A DP-ribosylating toxins. Other targets for endogenous ADP-ribosylation by procaryotes include glutamine synthetase in R. rubrum and Rhizobium meliloti and undefined proteins in Streptomyces griseus and Pseudomon as maltophila.