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 Mg(2+)-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 A resolution using synchrotron radiation. The crystals are hexagonal, belonging to the space group P6(1), with unit-cell parameters a = b = 86.89, c = 214.49 A, alpha = beta = 90.0, gamma = 120.0 degrees. 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 A(3) Da(-1) and a solvent content of 64.2%.