Trifluoroleucine resistance and regulation of alpha-isopropyl malate synthase in Saccharomyces cerevisiae.

Abstract

Seven spontaneous Saccharomyces cerevisiae mutants that express dominant resistance to 5,5,5-trifluoro-DL-leucine have been characterised at the molecular level. The gene responsible for the resistance was cloned from one of the mutants (FSC2.4). Determination of its nucleotide sequence showed that it was an allele of LEU4 (LEU4-1), the gene that encodes alpha-isopropyl malate synthase I (alpha-IPM synthase I), and that the mutation involved a codon deletion localised close to the 3' end of the LEU4 ORF. Six different point mutations--four transitions and two transversions--were found in the remaining mutants. Alpha-IPM synthase activity was found to be insensitive to feedback inhibition by leucine in five of the strains. In the other two the enzyme was resistant to Zn2+-mediated inactivation by Coenzyme A, a previously postulated control mechanism in energy metabolism; as far as we know, this represents the first direct in vivo evidence for this mechanism. The seven mutations define a region, the R-region, involved in both leucine feedback inhibition and in Zn2+-mediated inactivation by CoA. Deletion experiments involving the R-region showed that it is also necessary for enzyme activity.

• Authors: D Cavalieri, E Casalone, B Bendoni, G Fia, M Polsinelli, C Barberio
• Journal: Molecular & general genetics : MGG (Mol Gen Genet) Vol. 261 Issue 1 Pg. 152-60 (Feb 1999) ISSN: 0026-8925 [Print] Germany
• PMID: 10071221 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• RNA, Fungal
• Recombinant Fusion Proteins
• 5',5',5'-trifluoroleucine
• 2-Isopropylmalate Synthase
• Leucine
• Zinc
• Coenzyme A

Topics

• 2-Isopropylmalate Synthase (metabolism)
• Alleles
• Amino Acid Sequence
• Blotting, Northern
• Cloning, Molecular
• Coenzyme A (metabolism)
• DNA Mutational Analysis
• Drug Resistance, Microbial (genetics)
• Gene Deletion
• Genes, Fungal (genetics)
• Leucine (analogs & derivatives, metabolism, pharmacology)
• Molecular Sequence Data
• Mutation
• Plasmids (genetics)
• RNA, Fungal (genetics)
• Recombinant Fusion Proteins (genetics, metabolism)
• Saccharomyces cerevisiae (drug effects, enzymology, genetics)
• Sequence Alignment
• Sequence Analysis
• Sequence Homology, Amino Acid
• Transformation, Genetic
• Zinc (pharmacology)