Crystallization and preliminary X-ray analysis of lectin C from the roots of pokeweed (Phytolacca americana)

Abstract

Lectin C from the roots of pokeweed (Phytolacca americana) (PL-C; 13 747 Da, 126 amino-acid residues), which consists of three chitin-binding domains, was initially crystallized in two crystal forms. One form, obtained in the presence of 30%(w/v) PEG 4000, belongs to the tetragonal system. The other, obtained in the presence of 2.0 M ammonium sulfate, belongs to the rhombohedral system. Statistical analyses of the X-ray diffraction intensities showed that both crystals were twinned. Single crystals suitable for a diffraction experiment were obtained by the addition of 0.5%(v/v) dioxane to the latter precipitant solution. They belong to space group R3, with unit-cell parameters a = b = 104.1, c = 69.7 A, and diffract X-rays to 1.8 A resolution. A heavy-atom derivative crystal has been obtained and structure determination is presently ongoing using the SIRAS method.

Similarity between Protein–Protein and Protein–Carbohydrate Interactions, Revealed by Two Crystal Structures of Lectins from the Roots of Pokeweed

“…However, analyses of intensity distributions for the obtained crystals revealed that the crystals were heavily twinned (twin fraction; a ¼ 0.20). 49 Various additives were tried to avoid twinning. Single crystals suitable for the X-ray diffraction experiment were yielded in droplets prepared by mixing 1 ml of the protein solution with 1 ml of the reservoir solution containing 1.0% (v/v) dioxane.…”