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%.

The enzyme 3-dehydroquinase catalyzes the interconversion of 3-dehydroquinate and 3-dehydroshikimate. The enzymes are classified into two groups, type I and type II, which have different biochemical and biophysical properties and act with different mechanisms. The type II dehydroquinase of Helicobacter pylori, a dodecameric enzyme, was overexpressed in Escherichia coli. The recombinant protein has been crystallized at 296 K using polyethylene glycol (PEG) 4000 as a precipitant. Native X-ray diffraction data have been collected to 2.5 A resolution using synchrotron radiation. The crystals are cubic and belong to the space group P4(2)32, with unit-cell parameters a = b = c = 98.91 A. The asymmetric unit contains one subunit of recombinant type II dehydroquinase, with a corresponding V(M) of 2.18 A(3) Da(-1) and a solvent content of 43.6%.

Bacteriophage T4 deoxycytidylate hydroxymethylase (EC 2.1.2.8), a homodimer of 246‐residue subunits, catalyzes hydroxymethylation of the cytosine base in deoxycytidylate (dCMP) to produce 5‐hydroxymethyl‐dCMP. It forms part of a phage DNA protection system and appears to function in vivo as a component of a multienzyme complex called deoxyribonucleoside triphosphate (dNTP) synthetase. We have determined its crystal structure in the presence of the substrate dCMP at 1.6 Å resolution. The structure reveals a subunit fold and a dimerization pattern in common with thymidylate synthases, despite low (∼20

Deoxycytidylate hydroxymethylase from bacteriophage T4 is a homodimeric enzyme in which each polypeptide chain consists of 246 amino-acid residues. It has been crystallized in the presence of its substrate, deoxycytidine monophosphate, at room temperature using sodium citrate as precipitant. The crystals are monoclinic, belonging to space group C2, with unit-cell parameters a = 174.22, b = 53.12, c = 75.17 A, beta = 115.29 degrees. The asymmetric unit contains one homodimer, with a corresponding Vm of 2.65 A3 Da-1 and solvent content of 54%. Native diffraction data to 1.6 A resolution have been collected from two crystals using synchrotron radiation.