SOLUTION CONFORMATION OF RAPHANUS-SATIVUS ANTIFUNGAL PROTEIN-1 (RS-AFP1) BY H-1 NUCLEAR-MAGNETIC-RESONANCE RESONANCE ASSIGNMENTS, SECONDARYSTRUCTURE AND GLOBAL FOLD

The complete sequence specific assignment of the proton signals observ ed by two dimensional NMR spectroscopy was achieved for Raphanus sativ us Antifungal Protein 1 (Rs-AFP1), an antifungal protein isolated from radish seeds. The disulfide bridges are unambiguously assigned from t he observed inter-residue NOE connectivities between the cysteines. Re petitive secondary structure has been delineated from characteristic s ets of specific NOE contacts, (3)J(N alpha) coupling constants and ami de proton exchange rates. It is shown that Rs-AFP1 forms an alpha-heli x connected by two disulfide bridges to the central strand of an anti- parallel triple stranded beta-sheet, a motif known as the cysteine sta bilized alpha-helix motif.