Purification and characterization of a novel anti-fungal protein from Gastrodia elata

An anti-fungal protein GAFP-1 (Gastrodia anti-fungal protein, also called g astrodianin) was purified from Gastrodia elata Bl. flavida S. Chow (Orchida ceae), a parasitic plant on the fungus Armillaria mellea. It can inhibit th e hyphal growth of some phytopathogenic fungi such as Valsa ambiens, Rhizoc tonia solani, Gibberella zeae, Ganoderma lucidum and Botrytis cinerea in vi tro. GAFF-1 is a monomer with a molecular mass of 10 kDa and a pI of 8.45. The optimum pH for its inhibitory activity is 5.0 similar to 6.0. GAFF-1 is insensitive to high temperatures. It can preserve 75 % inhibitory activity after 30 min at 60 degrees C. Amino acid composition analysis revealed tha t GAFF-1 is rich in Asp (22.1 %), Gly (10.0 %) and Leu (9.4 %), and does no t contain any Pro. The amino acid sequence of the N-terminal was determined and found to share high homology with those of other lectins from orchids such as Listera ovata and Epipactis helleborine. GAFF-1 could not agglutina te trypsin-treated rabbit erythrocytes. It could bind to chitin, immobilize d mannose and N-acetylglucosamine in 50 mM sodium acetate buffer (pH 5.0) w ith 2 M ammonium sulfate. These data suggest that GAFF-1 could be a lectin- like protein with strong inhibitory activity against certain fungal pathoge ns. (C) Elsevier, Paris.