Parallel changes in catabolite repression of haem biosynthesis and cytochromes in repression-resistant mutants of Saccharomyces cerevisiae.
Effects of three mutant genes, CAT1-2d, cat2-1 and hex2-3, on catabolite repression of mitochondrial cytochromes and the first two enzymes of haem biosynthesis were compared. The CAT1-2d mutation gave no resistance to glucose, whereas cat2-1 endowed both cytochromes and 5-aminolaevulinate dehydratase with resistance, but did not alter the effect of glucose on 5-aminolaevulinate synthase. The hex2-3 mutation caused repression resistance of cytochromes and of the two haem biosynthetic enzymes. hex2-3 strains also accumulated intracellular 5-aminolaevulinate. Co-inheritance of the latter traits, sensitivity to maltose inhibition and ability to grow on raffinose in the presence of 2-deoxyglucose, demonstrated that the pleiotropic phenotype is a function of the single gene hex2-3. Revertants which grew on maltose regained sensitivity to deoxyglucose and exhibited normal sensitivity of cytochromes and haem biosynthesis enzymes to repression. Addition of the hex1-18 mutation, which renders cytochromes resistant to repression, to a cat2-1 strain did not produce the same effect on 5-aminolaevulinate synthase as hex2-3. It is concluded that repression patterns of haem and cytochrome biosynthesis are substantially affected by hex2-3 and cat2-1 but not by CAT1-2d.
Borralho
L M
LM
Departamento de Bioquímica, Universidade Federal do Rio de Janeiro, Cidade Universitária, Brasil.
Malamud
D R
DR
Panek
A D
AD
Tenan
M N
MN
Oliveira
D E
DE
Mattoon
J R
JR
D000624:5-Aminolevulinate Synthetase / Q000096:biosynthesis; D000332:Aerobiosis; D003580:Cytochromes / Q000096:biosynthesis*; D003847:Deoxyglucose / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D005246:Feedback; D005656:Fungal Proteins / Q000096:biosynthesis*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005800:Genes, Fungal; D005947:Glucose / Q000494:pharmacology; D006418:Heme / Q000096:biosynthesis*; D008320:Maltose / Q000494:pharmacology; D000623:Porphobilinogen Synthase / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics*
D003580:Cytochromes; D005656:Fungal Proteins; D006418:Heme; D008320:Maltose; D003847:Deoxyglucose; D000624:5-Aminolevulinate Synthetase; D000623:Porphobilinogen Synthase; D005947:Glucose