Plasminogen activator inhibitor 1 (PAI-1) in its active conformation: crystallization and preliminary X-ray diffraction data

Because of its intrinsic lability, wild-type plasminogen activator inhibito r 1 (PAI-1) cannot be crystallized in its active conformation. Therefore. a stable variant of PAT-I was used to retain the active conformation during crystallization. Four different crystallization conditions were evaluated i n detail and two major types of crystals were detected. Whereas solutions c onsisting of either (i) cacodylate and sodium acetate, (ii) lithium sulfate and polyethylene glycol 4K, or (iii) imidazole, sodium chloride and sodium potassium phosphate: buffer revealed thin platelet crystals a solution (iv ) containing ammonium acetate, citrate and polyethylene glycol JE; appeared to enhance the formation of clustered brush-like crystals. Crystals grown under condition (iii) were found to be suitable for X-ray data collection a nd consequent structural investigation. Data collection was 79.8% complete with a maximum resolution of 2.92 Angstrom. Importantly, PAI-1 retained its functional properties under all conditions.