Diphtheria toxin-resistant mutants of XXXX .

@entity375 @entity857 @entity73365
We developed a selection procedure based on the observation that diphtheria toxin kills spheroplasts of @entity375 (Murakami et al., Mol. Cell. Biol. 2:588-592, 1982); this procedure yielded mutants resistant to the in vitro action of the toxin. Spheroplasts of mutagenized @entity375 were transformed in the presence of diphtheria toxin, and the transformed survivors were screened in vitro for toxin-resistant @entity73365 . Thirty-one haploid @entity857 ribosylation-negative mutants comprising five complementation groups were obtained by this procedure. The mutants grew normally and were stable to prolonged storage. Heterozygous diploids produced by mating wild-type sensitive cells with the mutants revealed that in each case the resistant phenotype was recessive to the sensitive phenotype. Sporulation of these diploids yielded tetrads in which the resistant phenotype segregated as a single Mendelian character. From these observations, we concluded that these mutants are defective in the enzymatic steps responsible for the posttranslational modification of @entity73365 which is necessary for recognition by diphtheria toxin.
