Crystallization and preliminary X-ray crystallographic analysis of RNase HIII from Bacillus subtilis

The genome of Bacillus subtilis contains three different genes encoding RNase H homologs: RNases HI, HII and HIII. RNase HIII from B. subtilis degrades RNA in RNA–DNA hybrids in an Mg²⁺-dependent manner like Escherichia coli RNase HI. However, they belong to different classes; the former belongs to the `class II' or `large' RNase H family, while the latter belongs to the `class I' or `small' RNase H family. RNase HIII of B. subtilis has been overexpressed in E. coli and crystallized at 296 K using sodium formate as a precipitant. The native X-ray diffraction data have been collected to 2.8 Å resolution using synchrotron radiation. The crystals are hexagonal, belonging to the space group P6₁, with unit-cell parameters a = b = 86.89, c = 214.49 Å, α = β = 90.0, γ = 120.0°. A self-rotation function calculation indicated the presence of two monomers of the recombinant RNase HIII in the crystallographic asymmetric unit, giving a V_M of 3.43 ų Da⁻¹ and a solvent content of 64.2%.