title: Characterization of a Single-Stranded DNA-Binding-Like Protein from Nanoarchaeum equitans--A Nucleic Acid Binding Protein with Broad Substrate Specificity.
abstract: BACKGROUND
  SSB (single-stranded DNA-binding) proteins play an essential role in all living cells and viruses, as they are involved in processes connected with ssDNA metabolism. There has recently been an increasing interest in SSBs, since they can be applied in molecular biology techniques and analytical methods. Nanoarchaeum equitans, the only known representative of Archaea phylum Nanoarchaeota, is a hyperthermophilic, nanosized, obligatory parasite/symbiont of Ignicoccus hospitalis.
  
  
  RESULTS
  This paper reports on the ssb-like gene cloning, gene expression and characterization of a novel nucleic acid binding protein from Nanoarchaeum equitans archaeon (NeqSSB-like protein). This protein consists of 243 amino acid residues and one OB fold per monomer. It is biologically active as a monomer like as SSBs from some viruses. The NeqSSB-like protein displays a low sequence similarity to the Escherichia coli SSB, namely 10% identity and 29% similarity, and is the most similar to the Sulfolobus solfataricus SSB (14% identity and 32% similarity). The NeqSSB-like protein binds to ssDNA, although it can also bind mRNA and, surprisingly, various dsDNA forms, with no structure-dependent preferences as evidenced by gel mobility shift assays. The size of the ssDNA binding site, which was estimated using fluorescence spectroscopy, is 7 ± 1 nt. No salt-dependent binding mode transition was observed. NeqSSB-like protein probably utilizes a different model for ssDNA binding than the SSB proteins studied so far. This protein is highly thermostable; the half-life of the ssDNA binding activity is 5 min at 100 °C and melting temperature (T(m)) is 100.2 °C as shown by differential scanning calorimetry (DSC) analysis.
  
  
  CONCLUSIONS
  NeqSSB-like protein is a novel highly thermostable protein which possesses a unique broad substrate specificity and is able to bind all types of nucleic acids.
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Olszewski
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Jan
authors.initials: J
authors.lastname: Balsewicz
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Nowak
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Maciejewska
authors.affiliation: University of Wroclaw, Faculty of Biotechnology, Department of Protein Engineering, 50-138, Wrocław, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Cyranka-Czaja
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Zalewska-Piątek
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Rafał
authors.initials: R
authors.lastname: Piątek
authors.affiliation: Gdańsk University of Technology, Chemical Faculty, Department of Molecular Biotechnology and Microbiology, 80-233, Gdańsk, Poland.
authors.forename: Józef
authors.initials: J
authors.lastname: Kur
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D046588:Nanoarchaeota / Q000737:chemistry / Q000378:metabolism*; D055550:Protein Stability; D016415:Sequence Alignment; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D019843:Archaeal Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins