Members of this family assume a beta-gamma-crystallin fold [1,2], wherein nine beta-strands are connected by loop, and are separated into two sheets, each sheet forming the Greek key motif. The two Greek key motifs face each other in the global topology. The three-dimensional structure of the molecule is a 'sandwich'-shaped beta-barrel structure: hydrophobic side-chains are packed in the large interface area of the beta-sheets. In Streptomyces killer toxin-like protein domain confers a cytocidal effect to the toxin, causing cell death in both budding and fission yeasts, and morphological changes in yeasts and filamentous fungi [1]. This family also includes chitin-biding antifungal proteins [2-3].

1: NMR structure of Streptomyces killer toxin-like protein, SKLP: further evidence for the wide distribution of single-domain betagamma-crystallin superfamily proteins. Ohki SY, Kariya E, Hiraga K, Wakamiya A, Isobe T, Oda K, Kainosho M; J Mol Biol. 2001;305:109-120. PMID:11114251

2: Solution structure, backbone dynamics and chitin binding of the anti-fungal protein from Streptomyces tendae TU901. Campos-Olivas R, Horr I, Bormann C, Jung G, Gronenborn AM; J Mol Biol. 2001;308:765-782. PMID:11350173

3: Characterization of a novel, antifungal, chitin-binding protein from Streptomyces tendae Tu901 that interferes with growth polarity. Bormann C, Baier D, Horr I, Raps C, Berger J, Jung G, Schwarz H; J Bacteriol. 1999;181:7421-7429. PMID:10601197