Crystallization and preliminary crystallographic analysis of an Enterococcus faecalis repressor protein, CylR2, involved in regulating cytolysin production through quorum-sensing

CylR2 is one of two regulatory proteins associated with the quorum-sensing-dependent synthesis of cytolysin in the common pathogen Enterococcus faecalis. The protein was expressed with a C-terminal six-histidine tag and purified to homogeneity with a cobalt-affinity column followed by size-exclusion chromatography. Both native and SeMet proteins were produced and crystallized. Complete X-ray diffraction data sets were collected from a native crystal, which diffracted to 2.3 Å resolution, and a SeMet crystal, which diffracted to 2.1 Å. The crystals were tetragonal, belonging to space group P4₁ or P4₃, with unit-cell parameters a = b = 66.2, c = 40.9 Å, α = β = γ = 90°. Based on the calculated Matthews coefficient of 2.6 ų Da⁻¹ as well as analysis of anomalous difference Patterson maps, the asymmetric unit most likely contains two molecules of CylR2.