FEBS Advanced Lecture Course 97/02: "ATP Binding Cassette (ABC) Transporters: From Multidrug Resistance to Genetic Disease"
The ABC-Transporter Ste6 mediates
the secretion of the mating pheromone a-factor in the yeast Saccharomyces
cerevisiae. A Mata ste6 deletion strain produces mature
a-factor, but is not able to secrete the peptide.
After EMS mutagenesis about 30 mutants with increased b-galactosidase activity could be identified in a lacZ-filter test. The five mutants with the highest Ste6-LacZ activity were characterized further (Fig. 2). It could be demonstrated by pulse chase experiments, that wildtype Ste6 was stabilized in these mutants (Fig. 3). A screen with a cDNA library and backcross experiments prooved, that PEP4 was affected in mutant #81 (Fig. 4). The identification of a function which has already been shown to be involved in the degradation of Ste6 prooved the efficiency of the screen. Other mutants, in which Ste6 is even more stabilized than in pep4 cells, and in which the mutation has no effect in the proteolytic function of the vacuole, are currently being characterized.
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