Crystallization and preliminary X-ray crystallographic studies of a Lys49-phospholipase A₂ homologue from Bothrops pirajai venom complexed with rosmarinic acid

PrTX-I, a noncatalytic and myotoxic Lys49-phospholipase A₂ from Bothrops pirajai venom, was crystallized in the presence of the inhibitor rosmarinic acid (RA). This is the active compound in the methanolic extract of Cordia verbenacea, a plant that is largely used in Brazilian folk medicine. The crystals diffracted X-rays to 1.8 Å resolution and the structure was solved by molecular-replacement techniques, showing electron density that corresponds to RA molecules at the entrance to the hydrophobic channel. The crystals belong to space group P2₁2₁2₁, indicating conformational changes in the structure after ligand binding: the crystals of all apo Lys49-phospholipase A₂ structures belong to space group P3₁21, while the crystals of complexed structures belong to space groups P2₁ or P2₁2₁2₁.