Crystallization of biosynthetic arginine decarboxylase from Escherichia coli

Putrescine is the immediate precursor for the synthesis of polyamines and is normally generated by the action of ornithine decarboxylase. However, putrescine can also be produced by the conversion of arginine to agmatine by arginine decarboxylase (bADC) followed by the release of urea by agmatine ureohydrolase. Amino-acid sequence homology with the eukaryotic ornithine decarboxylases suggests that bADC may be a model for this group of decarboxylases. We report here the crystallization of arginine decarboxylase from E. coli. Crystals up to 1 mm in size are grown by vapor equilibration using Li2SO4 and polyethylene glycols as precipitants. The crystals exhibit diffraction maxima beyond 3 A resolution and belong to space group P41(3)212 with a = 192.4 and c = 121.0 A. These unit-cell dimensions together with the estimated density of the crystals suggest the presence of one tetramer of bADC (71 kDa subunit−1) per asymmetric unit (Vm = 2.0 A3 Da−1).