Isolation and characterization of the ATF2 gene encoding alcohol acetyltransferase II in the bottom fermenting yeast Saccharomyces pastorianus

The ATF2 gene encodes alcohol acetyltransferase II, which catalyses the syn thesis of isoamyl acetate from acetyl coenzyme A and isoamyl alcohol. To ch aracterize the ATF2 gene from the bottom fermenting yeast Saccharomyces pas torianus, the S. pastorianus ATF2 gene was cloned by colony hybridization u sing the S, cerevisiae ATF2 gene as a probe. When an atf1 null mutant strai n was transformed with a multi-copy plasmid carrying the S. pastorianus ATF 2 gene, the AATase activity of this strain was increased by 2.5-fold compar ed to the control. The S. pastorianus ATF2 gene has 99% nucleic acid homolo gy in the coding region and 100% amino acid homology with the S. cerevisiae ATF2 gene. Southern blot analysis of chromosomes separated by pulse-field gel electrophoresis indicated that the ATF2 gene probe hybridized to chromo some VII in S. cerevisiae and to the 1100 kb chromosome in S. pastorianus. As S. pastorianus is thought to be a hybrid of S. cerevisiae and S. bayanus , the S. bayanus-type gene, which has a relatively low level of homology wi th the S. cerevisiae-type gene, is also usually detected. Interestingly, an S. bayanus-type ATF2 gene could not be detected. These results suggested t hat the cloned ATF2 gene was derived from S. cerevisiae. Analysis using an ATF2-lacZ fusion gene in S. pastorianus showed that expression of the ATF2 gene was relatively lower than that of the ATF1 gene and that it is repress ed by aeration but activated by the addition of unsaturated fatty acids. Th e S. pastorianus ATF1, Lg-ATF1 and ATF2 Accession Numbers in the DDBJ Nucle otide Sequence Database are D63449, D63450 and D86480, respectively. Copyri ght (C) 1999 John Wiley & Sons, Ltd.