SAXS study of the snake toxin α-crotamine

α-crotamine is a small toxic protein (42 amino acid residues with three disulphide bridges) present in the venom of Crotallus durissus terrificus. Molecular parameters (Rg=13.7 A, S=3,000 A2, V=9,200 A3 and Dmax=40 A) were derived from SAXS curves obtained from a solution of this protein at pH=4.5. An excellent agreement between the experimental distance distribution curve and that calculated from a model consisting of two lobes linked by the Cys(18)-Cys(30) disulphide bridge.