The killer toxin SMK (salt-mediated killer) from the halotolerant yeast Pichia farinosa acts to kill sensitive strains of yeast. SMK exhibits maximum activity under conditions of acidic pH and high salt concentration. It is composed of two distinct subunits, alpha and beta, which tightly interact with each other under acidic conditions, jointly folding into an ellipsoidal single domain structure belonging to the alpha/beta-sandwich family. SMK assumes a similar folding topology to the fungal killer toxin KP4, forming two left-handed split beta/alpha/beta motifs which is rarely found in other toxins; hence, these toxins may be evolutionarily or functionally related [2]. SMK appears to function by associating with the membranes of sensitive cells [1]. This entry represents SMK alpha subunit.

1: Interaction of SMKT, a killer toxin produced by Pichia farinosa, with the yeast cell membranes. Suzuki C, Ando Y, Machida S; Yeast. 2001;18:1471-1478. PMID:11748724

2: The novel acidophilic structure of the killer toxin from halotolerant yeast demonstrates remarkable folding similarity with a fungal killer toxin. Kashiwagi T, Kunishima N, Suzuki C, Tsuchiya F, Nikkuni S, Arata Y, Morikawa K; Structure. 1997;5:81-94. PMID:9016714