Abstract
A new type of mutant unable to reduce 2, 3, 5-triphenyltetrazolium chloride (TTC) was isolated from miitagenized cells of Saccharomyces cerevisiae. These TTC- mutants were respirationcompetent although most TTC- mutants reported so far are respiration-deficient. The isolated mutants were also uracil auxotrophic, and genetic analysis indicated that a recessive mutation took place on a single gene tightly linked to the ura2 gene or in the ura2 gene in all these mutants. Moreover, we found that authentic ura mutants (ura1 to uraS) also exhibited the TTC- phenotype while other auxotrophic mutants tested were of the TTC+ phenotype. These findings suggest that yeast cells have a TTCreduction system related to uracil metabolism besides that related to respiratory potential.
