The Sso7d protein of Sulfolobus solfataricus: in vitro relationship among different activities
ANNAMARIA GUAGLIARDI,1,2 LAURA CERCHIA 1 and MOSÈ ROSSI 1,3
1 Dipartimento di Chimica Biologica, Università Federico II di Napoli, Via Mezzocannone 16, 80134 Napoli, Italy
2 Author to whom correspondence should be addressed ([email protected])
3 Istituto di Biochimica delle Proteine ed Enzimologia, CNR, Via Marconi 10, 80125 Napoli, Italy
Received October 22, 2001; accepted January 8, 2002; published online March 5, 2002
The physiological role of the nonspecific DNA-binding protein Sso7d from the crenarchaeon Sulfolobus solfataricus is unknown. In vitro studies have shown that Sso7d promotes annealing of complementary DNA strands (Guagliardi et al. 1997), induces negative supercoiling (Lopez-Garcia et al. 1998), and chaperones the disassembly and renaturation of protein aggregates in an ATP hydrolysis-dependent manner (Guagliardi et al. 2000). In this study, we examined the relationships among the binding of Sso7d to double-stranded DNA, its interaction with protein aggregates, and its ATPase activity. Experiments with 1-anilinonaphthalene-8-sulfonic acid as probe demonstrated that exposed hydrophobic surfaces in Sso7d are responsible for interactions with protein aggregates and double-stranded DNA, whereas the site of ATPase activity has a non-hydrophobic character. The interactions of Sso7d with double-stranded DNA and with protein aggregates are mutually exclusive events, suggesting that the disassembly activity and the DNA-related activities of Sso7d may be competitive in vivo. In contrast, the hydrolysis of ATP by Sso7d is independent of the binding of Sso7d to double-stranded DNA or protein aggregates.
ATP hydrolysis, DNA-binding protein, hydrophobic protein interaction, protein aggregation.