X-ray crystallographic analysis of pokeweed antiviral protein-II after reductive methylation of lysine residues

Pokeweed antiviral protein II (PAP-II) is a naturally occurring protein iso lated from early summer leaves of the pokeweed plant (Phytolacca americana) . PAP-II belongs to a family of ribosome-inactivating proteins which cataly tically deadenylate ribosomal and viral RNA. The chemical modification of P AP-II by reductive methylation of its lysine residues significantly improve d the crystal quality for X-ray diffraction studies. Hexagonal crystals of the modified PAP-II, with unit cell parameters a = b = 92.51 Angstrom, c = 79.05 Angstrom were obtained using 1.8 M Na/K phosphate as the precipitant. These crystals contained one enzyme molecule per asymmetric unit and diffr acted up to 2.4 Angstrom when exposed to a synchroton source, (C) 2000 Acad emic Press.