Crystallization and preliminary X-ray investigation of holotryptophanases from Escherichia coli and Proteus vulgaris.

Crystals of Proteus vulgaris holotryptophanase have been grown by the hanging-drop technique using polyethylene glycol 4000 as precipitant in the presence of monovalent cations K+ or Cs+. Orthorhombic crystals (P2(1)2(1)2(1)) grown with Cs+ have unit cell parameters a = 115.0 A, b = 118.2 A and c = 153.7 A and diffract to 1.8 A. There are four subunits of the tetrameric molecule in the asymmetric unit. Native data have been collected to 2.5 A resolution. The 3.4 A data were collected from tetragonal crystals of Escherichia coli holotryptophanase grown under conditions described by Kawata et al. (1991). The molecular replacement solution for this crystal form has been found using tyrosine phenol-lyase coordinates. The correct enantiomorph is P4(3)2(1)2. There are two subunits in the asymmetric unit.