Members of this fungal family of toxins specifically inhibit voltage-gated calcium channels in mammalian cells. They adopt an alpha/beta-sandwich structure, comprising a five-stranded antiparallel beta-sheet with two antiparallel alpha-helices lying at approximately 45 degrees to these strands [1].

1: Structure and function of a virally encoded fungal toxin from Ustilago maydis: a fungal and mammalian Ca2+ channel inhibitor. Gu F, Khimani A, Rane SG, Flurkey WH, Bozarth RF, Smith TJ; Structure. 1995;3:805-814. PMID:7582897