A yeast gene necessary for bud-site selection encodes a protein similar to insulin-degrading enzymes

Abstract

CELLS of the yeast Saccharomyces cerevisiae choose bud sites in a non-random spatial pattern that depends on mating type: axial for haploid cells and bipolar for a/α diploid cells1,2. We identified a mutant yeast, axi1, in which the budding pattern is altered from axial to bipolar. Expression of the AXLI gene is repressed in a/a diploid cells. With the ectopic expression of AXL1, a/α cells exhibited an axial budding pattern, thus AXL1 is a key morphological determinant that distinguishes the budding pattern of haploid cells from that of a/α diploid cells2. AXL1 encodes a protein similar in sequence to the human and Drosophila insulin-degrading enzymes3,4 and to the Escherichia coli ptr gene product5. The axial budding pattern might result from degradation of a target protein by the putative Axil protease.