Purification, crystallization and preliminary X-ray diffraction analysis of the Trichoderma reesei hydrophobin HFBI

Hydrophobins are fungal proteins that are capable of altering the hydrophobicity of surfaces by self-assembly at hydrophilic-hydrophobic interfaces. Here, the growth of hydrophobin crystals suitable for X-ray crystallography is reported. The hydrophobin HFBI from Trichoderma reesei was crystallized by vapour diffusion in hanging drops in 30% PEG 4000, 0.1 M sodium citrate pH 4.3 buffer containing 0.2 M ammonium acetate and CYMAL-5 detergent (initial concentration of 2.4 mM). HFBI crystals are hexagonal and belong to space group P6₁ (or P6₅), with unit-cell parameters a = b = 45.9, c = 307.2 Å. The HFBI used in the crystallization experiments was purified from fungal cell walls.