Preliminary crystallographic characterization of PrnB, the second enzyme in the pyrrolnitrin biosynthetic pathway

Pyrrolnitrin is the active ingredient of drugs for the treatment of superficial fungal infections and was used as a lead structure for the development of fludioxonil. It is an effective agent for plant diseases caused by the fungal pathogen Rhizoctonia solani. Pyrrolnitrin is made in four steps, the second of which, catalyzed by PrnB, is a novel chemical rearrangement of 7-chlorotryptophan. PrnB was overproduced in Pseudomonas fluorescens (BL915) and well diffracting crystals were obtained of a triple cysteine-to-serine mutant by sitting-drop vapour diffusion. Crystals grown in the presence of l-7-chlorotryptophan, d-­tryptophan and l-tryptophan are reported. Data sets for each are reported with high-resolution limits of 2.0, 1.75 and 1.75 Å, respectively. Two crystals (PrnB in the presence of d-tryptophan and l-7-chlorotryptophan) belong to space group C2 with similar unit-cell parameters (a = 68.6, b = 79.5, c = 92.7 Å, α = γ = 90.0, β = 103.8°). Crystals grown in the presence of l-­tryptophan belong to space group C222(1) and have unit-cell parameters a = 67.7, b = 80.1, c = 129.5 Å. All crystals contain a monomer in the asymmetric unit.