Crystallization and preliminary X-ray analysis of neuropsin, a serine protease expressed in the limbic system of mouse brain

Neuropsin (M(r) 25 032) is a serine protease expressed in the limbic system of mouse brain. It has been implicated in various neurological processes including formation of memory and may be important as a drug target in the treatment of epilepsy. The recombinant protein was produced using a baculovirus expression system and was purified. Two crystal forms were obtained by a hanging-drop vapor-diffusion method with polyethylene glycol. Preliminary X-ray crystallographic analysis revealed that crystal form I belongs to triclinic space group P1 with unit cell dimensions a = 97.16 Å, b = 97.12 Å, c = 46.75 Å and α = 99.17°, β = 99.77°, γ = 117.35°. Self- rotation function analysis of these data of form I indicates the position of a noncrystallographic threefold axis. There are six molecules in the crystallographic asymmetric unit. Crystal form II also belongs to triclinic space group P1 but has unit cell dimensions of a = 38.40 Å, b = 55.16 Å, c = 65.37 Å and α = 95.38°, β = 89.98°, γ = 110.46°with two molecules in the crystallographic asymmetric unit. Form II has a noncrystallographic twofold axis. Intensity data to 3.1 Å resolution for form I and to 2.2 resolution for form II have been collected.