Kluyveromyces lactis killer toxin inhibits adenylate cyclase of sensitive yeast cells

Publisher Website
Google Scholar
Abstract
K1 killer toxin secreted by the K+1 strain of Saccharomyces cerevisiae, has been well characterized1,2. It is a simple protein of molecular weight (MW) 11,470 (ref. 3), encoded by a double-stranded, linear RNA plasmid, called MRNA, of MW 1.1–1.7 × 106 (refs 4–6). It is lethal to sensitive Saccharomyces cerevisiae which does not carry M RNA. Leakage of K+ and ATP is the first distinct response in sensitive cells7–9, and the toxic action is thought to be due to its action as a protonophore10,11 or K+ ionophore2. Recently, a further killer toxin has been found in Kluyveromyces lactis IFO 1267, and it is associated with the presence of the double-stranded linear DNA plasmids, pGK1-1 (MW 5.4 × 106) and pGK1-2 (MW 8.4 × 106)12. It has been shown, by curing pGK1-1 or deletion mapping, that the structural gene for the killer toxin and immunity-determining gene reside on the smaller plasmid13,14. Moreover, the plasmids could be transferred from K. lactis to S. cerevisiae by protoplast fusion and protoplast transformation13,15. As the K. lactis toxin is encoded by a DNA plasmid and has a relatively wider action spectrum than K1 killer toxin12,13, the mode of action of the toxin is highly interesting. Here we report that K. lactis toxin inhibits adenylate cyclase in sensitive yeast cells and brings about arrest of the cells at the G1 stage.