ADP-RIBOSYLATION REACTIONS IN SULFOLOBUS-SOLFATARICUS, A THERMOACIDOPHILIC ARCHAEON

An ADP-ribosylating system was detected in a crude homogenate from Sul folobus solfataricus, a thermophilic archaeon, optimally growing at 87 degrees C. The archaeal ADP-ribosylation reaction was time-, temperat ure- and NAD-dependent. It proved to be highly thermostable, with abou t 30% decrease of C-14 incorporation from [C-14]NAD on incubation at 8 0 degrees C for up to 24 h. The main reaction product was found to be mono-ADP-ribose. Testing both [adenine-C-14(U)]NAD and [adenine-C-14(U )]ADPR as substrates, it was found that acceptor proteins were modifie d by ADP-ribose both enzymatically, via ADP-ribosylating enzymes, and via chemical attachment of free ADP-ribose, likely produced by NAD gly cohydrolase activity. The synthesis of ADP-ribose-protein complexes wa s shown to involve mainly accepters with molecular masses in the 40-10 0 kDa range, as determined by electrophoresis on polyacrylamide gel in the presence of sodium dodecyl sulphate.