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 P 4 1 2 1 2, with unit‐cell parameters a = b = 95.42, c = 124.50 Å. The asymmetric unit contains one sHAI‐1 molecule.