Cysteine biosynthesis in Saccharomyces cerevisiae: mutation that confers cystathionine beta-synthase deficiency.
The cys2-1 mutation of Saccharomyces cerevisiae was originally thought to confer cysteine dependence through a serine O-acetyltransferase deficiency. In this study, we show that cys2-1 strains lack not only serine O-acetyltransferase but also cystathionine beta-synthase. However, a prototrophic strain was found to be serine O-acetyltransferase deficient because of a mutation allelic to cys2-1. Moreover, revertants obtained from cys2-1 strains had serine O-acetyltransferase but not cystathionine beta-synthase, whereas transformants obtained by treating a cys2-1 strain with an S. cerevisiae genomic library had cystathionine beta-synthase but not serine O-acetyltransferase. From these observations, we conclude that cys2-1 (serine O-acetyltransferase deficiency) accompanies a very closely linked mutation that causes cystathionine beta-synthase deficiency and that these mutations together confer cysteine dependence. This newly identified mutation is named cys4-1. These results not only support our previous hypothesis that S. cerevisiae has two functional cysteine biosynthetic pathways but also reveal an interesting gene arrangement of the cysteine biosynthetic system.
Ono
B
B
Laboratory of Environmental Hygiene Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Shirahige
Y
Y
Nanjoh
A
A
Andou
N
N
Ohue
H
H
Ishino-Arao
Y
Y
D000123:Acetyltransferases / Q000235:genetics; D000483:Alleles; D003433:Crosses, Genetic; D003541:Cystathionine beta-Synthase / Q000235:genetics*; D003545:Cysteine / Q000096:biosynthesis*; D005796:Genes; D005800:Genes, Fungal; D005838:Genotype; D006836:Hydro-Lyases / Q000235:genetics*; D008715:Methionine / Q000096:biosynthesis; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D051050:Serine O-Acetyltransferase
D008715:Methionine; D000123:Acetyltransferases; D051050:Serine O-Acetyltransferase; D006836:Hydro-Lyases; D003541:Cystathionine beta-Synthase; D003545:Cysteine