Recombinant hepatocyte growth factor activator inhibitor 1: expression in Drosophila S2 cells, purification and crystallization.

Hepatocyte growth factor activator inhibitor 1 (HAI-1) is a multi-domain membrane-associated protease inhibitor that potently inhibits a variety of serine proteases such as hepatocyte growth factor activator and matriptase. Different truncates of HAI-1 show varying potencies for inhibition of target proteases, suggesting that the domain organization of HAI-1 plays a critical role in its function. Here, the soluble full-length extracellular part of HAI-1 (sHAI-1) was expressed using the Drosophila S2 insect-cell expression system. Diffraction-quality crystals of sHAI-1 were produced using ammonium sulfate as precipitant. The crystal diffracted to 3.8 Å resolution and belonged to space group P422, with unit-cell parameters a = b = 95.42, c = 124.50 Å. The asymmetric unit contains one sHAI-1 molecule.