Evolution of three-finger toxins - a versatile mini protein scaffold.

Among snake venom toxins, three-finger toxins - a superfamily of nonenzymatic proteins - are found in the venoms of all families of snakes. They share a common structure of three β-stranded loops extending from a central core containing all four conserved disulfide bonds. Despite the similar structural fold, they exhibit a wide variety of biological effects. This review describes briefly the structure-function relationships and evolution of this group of toxins. The functional sites in these šsibling' toxins are located on various segments of the molecular surface. This group of mini proteins appears to evolve through a combination of accelerated rate of exchange of segments as well as point mutations in exons.