Crystallization and X-ray diffraction studies of arginine kinase from the white Pacific shrimp Litopenaeus vannamei

Crystals of an unligated monomeric arginine kinase from the Pacific whiteleg shrimp Litopenaeus vannamei (LvAK) were successfully obtained using the microbatch method. Crystallization conditions and preliminary X-ray diffraction analysis to 1.25 Å resolution are reported. Data were collected at 100 K on NSLS beamline X6A. The crystals belonged to space group P2₁2₁2₁, with unit-cell parameters a = 56.5, b = 70.2, c = 81.7 Å. One monomer per asymmetric unit was found, with a Matthews coefficient (V_M) of 2.05 Å³ Da^-1 and 40% solvent content. Initial phases were determined by molecular replacement using a homology model of LvAK as the search model. Refinement was performed with PHENIX, with final R_work and R_free values of 0.15 and 0.19, respectively. Biological analysis of the structure is currently in progress.