H-1-NMR STRUCTURE OF AN ANTIFUNGAL GAMMA-THIONIN PROTEIN SI-ALPHA-1 -SIMILARITY TO SCORPION TOXINS

The three-dimensional structure of the Sorghum bicolor seed protein ga mma-thionin SI alpha 1 has been determined by 2D H-1 nuclear magnetic resonance (NMR) spectroscopy. The secondary structure of this 47-resid ue antifungal protein with four disulphide bridges consists of a three -stranded antiparallel sheet and one helix. The helix is tethered to t he sheet by two disulphide bridges which link two successive turns of the helix to alternate residues i, i + 2 in one strand. Possible bindi ng sites for antifungal activity are discussed. The same fold has been observed previously in several scorpion toxins. Proteins 32:334-349, 1998. (C) 1998 Wiley-Liss, Inc.