Single-stranded DNA bound to bacterial cold-shock proteins: preliminary crystallographic and Raman analysis

The cold-shock response has been described for several bacterial species. It is characterized by distinct changes in intracellular protein patterns whereby a set of cold-shock-inducible proteins become abundant. The major cold-shock proteins of Bacillus subtilis (Bs-­CspB) and Bacillus caldolyticus (Bc-Csp) are small oligonucleotide/oligosaccharide-binding (OB) fold proteins that have been described as binding single-stranded nucleic acids. Bs-CspB (M_r = 7365) and Bc-Csp (M_r = 7333) were crystallized in the presence of the deoxyhexanucleotide (dT)₆. Crystals of (dT)₆ with Bs-CspB grew in the orthorhombic space group C222₁, with unit-cell parameters a = 49.0, b = 53.2, c = 77.0 Å. Crystals with Bc-Csp grew in the primitive orthorhombic space group P2₁2₁2, with unit-cell parameters a = 74.3, b = 64.9, c = 31.2 Å. These crystals diffract to maximal resolutions of 1.78 and 1.29 Å, respectively. The presence of protein and DNA in the crystals was demonstrated by Raman spectroscopy.