Preliminary crystallographic analysis of RraB from Escherichia coli

RraB, an inhibitor of the essential endoribonuclease RNE in Escherichia coli, is essential in regulating the abundance of RNA by directly interacting with RNE. In this study, RraB from E. coli was cloned, expressed, purified and crystallized. The crystals belonged to space group P2₁2₁2₁, with unit-cell parameters a = 58.59, b = 58.34, c = 156.95 Å. X-ray diffraction data were collected to a resolution of 2.9 Å. Analysis of the native Patterson map revealed a peak of ∼37% the height of the origin peak in the ν = 0.5 Harker section, suggesting twofold noncrystallographic symmetry parallel to the b crystallographic axis. The Matthews coefficient and the solvent content were estimated to be 4.09 ų Da⁻¹ and 69.94%, respectively, assuming the presence of two molecules in the asymmetric unit.