Characterization, crystallization and preliminary crystallographic analysis of human recombinant cyclooxygenase-2

Purified recombinant membrane apoprotein cyclooxygenase-2 (COX-2) has been reconstituted with heme and characterized. The holoprotein has been crystallized in complex with the selective inhibitor CGP 28238 [6-(2,4-difluorophenoxy)-5- methylsulfonylamino-l-indanone] by the sitting-drop method of vapor diffusion using polyethylene glycol 2000 monomethyl ether as precipitant, in the presence of the nonionic detergent β-octylglucoside. The crystals are orthorhombic, belonging to the space group P2₁2₁2 with cell dimensions a = 209.56, b = 71.28 and c = 93.82 Å, and diffract to 2.5 Å resolution. The asymmetric unit contains two COX-2 monomers, as confirmed by the molecular replacement solution and in agreement with the dimeric structure of the detergent-solubilized protein found with dynamic light scattering and size-exclusion chromatography. Structural work is in progress.