To study the biochemical properties of SSB from Psychrobacter arcticus (ParSSB), we have cloned the ssb genes obtained by PCR and have developed Escherichia coli overexpression systems. The gene consists of an open reading frame of 642 nucleotides encoding SSB protein of 213 amino acids with a calculated molecular mass of 22.8 kDa. The amino-acid sequence of ParSSB exhibits 49% identity and 57% similarity to Escherichia coli SSB. In analysis by gel filtration chromatography we show that ParSSB is functional as homooctamer, a structure as yet unlisted in published SSB proteins. Each monomer encodes one single-stranded DNA binding domains (OB-fold). In fluorescence titrations with poly(dT), it binds single-stranded DNA with a binding site size of about 22 - 34 nt depending on the salt concentration, and fluorescence is quenched by about 95%. Thermostability with half-lives of about 15 min at 100°C makes SSB from Psychrobacter arcticus the most thermostable SSB protein among psychrophilic and mesophilic bacteria indentified to date. ParSSB is more thermostable even than commonly-used SSB from T. aquaticus and T. thermophilus. The rare, high thermostability of this cold-adapted protein and the homooctameric structure, which is unique among all known pro- and eucariotic single-stranded DNA binding proteins, could prove to be useful in various molecular biology techniques.
Authors
- Marta Nowak,
- Marcin (009) Olszewski,
- prof. dr hab. Józef Kur link open in new tab
Additional information
- Category
- Inne
- Type
- supllement, wydanie specjalne, dodatek
- Language
- angielski
- Publication year
- 2011
