Baumann H, Knapp S, Lundbäck T, Ladenstein R, Härd T
Center for Structural Biochemistry, Karolinska Institutet, NOVUM, Huddinge, Sweden.
Nat Struct Biol. 1994 Nov;1(11):808-19. doi: 10.1038/nsb1194-808.
The archaeon Sulfolobus solfataricus expresses large amounts of a small basic protein, Sso7d, which was previously identified as a DNA-binding protein possibly involved in compaction of DNA. We have determined the solution structure of Sso7d. The protein consists of a triple-stranded anti-parallel beta-sheet onto which an orthogonal double-stranded beta-sheet is packed. This topology is very similar to that found in eukaryotic Src homology-3 (SH3) domains. Sso7d binds strongly (Kd < 10 microM) to double-stranded DNA and protects it from thermal denaturation. In addition, we note that epsilon-mono-methylation of lysine side chains of Sso7d is governed by cell growth temperatures, suggesting that methylation is related to the heat-shock response.
