Purification, crystallization and preliminary X-ray diffraction analysis of the 23S rRNA methyltransferase RlmJ from Escherichia coli

The 23S rRNA methyltransferase RlmJ from E. coli has been cloned, expressed, purified and crystallized. X-ray diffraction data to 1.85 Å resolution have been collected from the apo RlmJ crystals. Methyltransferase RlmJ uses the cofactor S-adenosylmethionine to methylate the exocyclic nitrogen N6 of nucleotide A2030 in 23S rRNA during ribosome assembly in Escherichia coli. RlmJ with a C-terminal hexahistidine tag was overexpressed in E. coli and purified as a monomer using Ni²⁺-affinity and size-exclusion chromatography. The recombinant RlmJ was crystallized using the sitting-drop vapour-diffusion method and a full data set was collected to 1.85 Å resolution from a single apo crystal. The crystals belonged to space group P2₁, with unit-cell parameters a = 46.9, b = 77.8, c = 82.5 Å, β = 104°. Data analysis suggested two molecules per asymmetric unit and a Matthews coefficient of 2.20 ų Da⁻¹