Properties of a hydrophobin isolated from the mycoparasitic fungus Verticillium fungicola

Abstract

Verticillium fungicola, isolated from Agaricus bisporus (commercial mushroom), produced significant extracellular hydrophobin when grown for 7 days in a static liquid culture of synthetic minimal medium. The hydrophobin was purified by precipitation with ammonium sulphate (80% saturation), Sephadex G-100 gel filtration, and hydroxyapatite column chromatography. The purified protein yielded a single band in polyacrylamide gel electrophoresis under native conditions, with an apparent molecular mass of 70 ± 4 kDa, and also another single band in SDS–PAGE, with a molecular mass of 7 ± 3 kDa. Molecular mass determined with matrix-assisted laser desorption ionization–mass spectrometry (MALDI–MS) resulted in 7563.9 m/z. The same protein was extracted from the V. fungicola mycelium. Analysis of the amino acid composition revealed the presence of about 50% hydrophobic residues, detecting at least six cysteines, evaluated as cystines, and no free sulfhydryl groups. The protein did not show any glycosylation. On the basis of similarities in hydropathy patterns and solubility characteristics, V. fungicola hydrophobin can be included as a new member of Class II hydrophobins.Key words: Verticillium fungicola, Agaricus bisporus, hydrophobin, mycoparasitism.