Purification and characterization of tobacco pathogenesis-related protein PR-5d, an antifungal thaumatin-like protein

Cultured tobacco cells accumulate several pathogenesis-related proteins. A neutral PR-5 protein, PR-5d, was purified to homogeneity from such cells. PR-Sd has highly hydrophobic characteristics, but hydropathy analysis of its primary structure did not show a hydrophobic domain. In a series of bioassays, purified PR-5d showed inhibitory activity against several phytopathogenic and non-phytopathogenic fungi as do other members of the PR-5 protein family. To study the antifungal mechanism based on three dimensional structure of PR-5d, purified PR-5d was crystallized. The preliminary X-ray analysis of the crystal revealed that the crystals belong to space group C2, with cell dimensions a=80.2 Angstrom, b=63.8 Angstrom, c=45.7 Angstrom, and beta = 107.2 degrees, and diffract at least 1.8 Angstrom resolution.