Purification, crystallization and preliminary X-ray diffraction analysis of the Whirly domain of StWhy2 in complex with single-stranded DNA.

StWhy1 and StWhy2 are members of the Whirly family of single-stranded DNA (ssDNA) binding proteins. To understand the mode of binding of the Whirly proteins to single-stranded DNA, crystals of the Whirly domains of both StWhy1 and StWhy2 in complex with single-stranded DNA were obtained by the hanging-drop vapour-diffusion method. The diffraction patterns of the StWhy1-ssDNA complex crystals displayed severe anisotropy and were of low resolution, making them unsuitable for structure determination. In contrast, the crystals of the StWhy2-ssDNA complex diffracted isotropically to 2.20 A resolution. The crystallization and data collection to 2.20 A resolution of StWhy2 in the free form are also reported.