The ADP-ribosylation of S. solfataricus Sso7 modulates protein/DNA interactions in vitro.

The 7 kDa Sso7 is a basic protein particularly abundant in Sulfolobus solfataricus and is involved in 28 DNA assembly. This protein undergoes in vitro ADP-ribosylation by an endogenous poly(ADP-ribose) 29 polymerase-like enzyme. The circular dichroism spectrum of purified ADP-ribosylated Sso7 shows 30 that this modification stabilizes the prevalent protein b-conformation, as suggested by shifting of 31 negative ellipticity minimum to 220 nm. Moreover, a short ADP-ribose chain (up to 6-mers) bound 32 to Sso7 is able to reduce drastically the thermoprotective and DNA condensing ability of the protein, 33 suggesting a possible regulatory role of ADP-ribosylation in sulfolobal DNA organization. 34 _ 2009 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies. 35