Expression, purification and preliminary X-ray crystallographic analysis of cyanobacterial biliverdin reductase

Biliverdin reductase (BVR) catalyzes the conversion of biliverdin IX α to bilirubin IX α with concomitant oxidation of an NADH or NADPH cofactor. This enzyme also binds DNA and enhances the transcription of specific genes. Recombinant cyanobacterial BVR was overexpressed in Escherichia coli, purified and crystallized. A native data set was collected to 2.34 Å resolution on beamline BL38B1 at SPring-8. An SeMet data set was collected from a microcrystal (300 × 10 × 10 µm) on the RIKEN targeted protein beamline BL32XU and diffraction spots were obtained to 3.0 Å resolution. The native BVR crystal belonged to space group P2₁2₁2₁, with unit-cell parameters a = 58.8, b = 88.4, c = 132.6 Å. Assuming that two molecules are present in the asymmetric unit, V_M (the Matthews coefficient) was calculated to be 2.37 ų Da⁻¹ and the solvent content was estimated to be 48.1%. The structure of cyanobacterial BVR may provide insights into the mechanisms of its enzymatic and physiological functions.