INTRACELLULAR EXPRESSION OF TOXIC SHOCK SYNDROME TOXIN-1 IN SACCHAROMYCES-CEREVISIAE

In order to search for an occult cytotoxic enzymatic activity of the t oxic shock syndrome toxin 1 (TSST-1), we placed the gene encoding TSST -1 (tstH) under the control of an inducible promoter in the eukaryotic yeast Saccharomyces cerevisiae. Under similar circumstances, the know n bacterial enzymatic cytotoxins Shiga-like toxin and diphtheria toxin are both highly lethal to the yeast host. Although full-length stable TSST-1 was demonstrated within the yeast cells and although it retain ed mitogenicity for human T cells, it had no apparent effect on the ye ast cells' growth kinetics or on their gross morphology. Retrieval and sequencing of the toxin gene revealed the wild-type sequence througho ut, thus demonstrating that the apparent lack of toxicity for the yeas t cells was not due to a serendipitous attenuating mutation within the coding region of the toxin gene. Similar results obtained after a sec ond transformation of the same strain and after transformation of an u nrelated strain demonstrate that neither chance permissive host mutati on nor intrinsic host resistance was likely to have obscured an existi ng cytotoxic property of TSST-1. We conclude that TSST-1 probably does not possess a discrete enzymatic property cytotoxic for eukaryotic ce lls.