Abstract
Abstract Single-stranded DNA binding protein (SSB) plays an important role in DNA metabolism, such as DNA replication, repair and recombination. The N-terminal domain of SSB forms an oligonucleotides/oligosaccharides binding (OB) fold, which function as single-stranded DNA (ssDNA) binding domain. The C-terminal conserved tail is supposed to participate in the protein-protein interaction. The crystal structure of C-terminal truncated SSB from Helicobacter pylori (residues 1-134, HpSSB134) bound to two dT(pT)34 [HpSSB134-dT(pT)34] was determined by molecular replacement method at 2.3 Å. The ssDNA wraps around four subunits of HpSSB134 by the electrostatic and hydrophobic stacking interactions. Four aromatic residues, Phe37, Phe50, Phe56 and Trp84, interact with the base of ssDNA by stacking arrangement. Meanwhile, four basic residues, Arg10, Arg36, Arg54 and Arg94, on the surface of HpSSB134 form a significant electrostatic path corresponding to the ssDNA binding.