Branched chain amino acid regulation of the ILV2 locus in Saccharomyces cerevisiae

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Wei Xiao ◽  
Gerald H. Rank
Keyword(s):  
Amino Acid ◽  
Acetolactate Synthase ◽  
Multiple Control ◽  
Isoleucine Leucine ◽  
Acid Sensitivity ◽  
Cis Acting ◽  
General Amino Acid Control ◽  
Branched Chain Amino Acid ◽  
Branched Chain ◽  
Unusual Phenotype

Mutant regulatory loci of the branched pathway for the biosynthesis of isoleucine–valine and leucine were identified with the unusual phenotype of an amino acid dependent auxotrophy. Two mutant loci, bcs1 and bcs2, conferred branched chain amino acid sensitivity and showed independent segregation. Linkage studies defined bcs1 as a cis-acting regulatory site of ILV2 (SMR1). ILV2 upstream deletion analyses and high-copy transformation of the positive regulatory locus LEU3 ruled out the possibility of LEU3 protein binding palindromes mediating the branched chain amino acid dependent auxotrophy. In the presence of leucine and valine, the general amino acid control system (GCN4) was epistatic to bcs1 and bcs2, and under nonstarvation conditions GCN4 strains showed an increased acetolactate synthase activity over gcn4 strains. Thus in addition to general regulation of ILV2, GCN4 functions in basal level expression when the locus is subject to specific repression by pathway end product.Key words: yeast, isoleucine, leucine, valine pathway, amino acid sensitivity, gene regulation, multiple control.

Repression of the Branched-Chain Amino Acid Biosynthetic Enzymes in Developing Conidia and Mycelia of Neurospora

1974 ◽  
Vol 52 (10) ◽  
pp. 822-829 ◽  
Author(s):  
Andrés J. Jobbágy ◽  
Robert P. Wagner
Keyword(s):  
Amino Acid ◽  
Neurospora Crassa ◽  
Enzymic Activity ◽  
Logarithmic Phase ◽  
Biosynthetic Enzymes ◽  
Wild Type ◽  
Isoleucine Leucine ◽  
Branched Chain Amino Acid ◽  
End Products ◽  
Branched Chain

During germination of the conidia of wild type Neurospora crassa, the enzymes of the isoleucine–valine pathway increase in activity. This increase is partially repressed in the presence of a combination of exogenous isoleucine, leucine, and valine. Repressed levels of enzymic activity are also observed in mycelium during the logarithmic phase of growth. In both cases, isoleucine and leucine together are almost as effective without valine as when the three are present together. The synthesis of these enzymes does appear to be affected by their end products but not to the extent exhibited in bacteria.

Acetolactate Synthase and Ketol-Acid Reductoisomerase: Targets for Herbicides Obtained by Screening and de novo Design

1990 ◽  
Vol 45 (5) ◽  
pp. 544-551 ◽  
Author(s):  
John V. Schloss ◽  
Ann Aulabaugh
Keyword(s):  
Amino Acid ◽  
Acetolactate Synthase ◽  
Amino Acid Biosynthesis ◽  
Specific Gene ◽  
Selective Inhibitors ◽  
Acid Biosynthesis ◽  
Threonine Deaminase ◽  
Screening Techniques ◽  
Branched Chain Amino Acid ◽  
Branched Chain

Several major classes of herbicides, discovered by conventional screening techniques, have been found to inhibit the first common enzyme of branched-chain amino acid biosynthesis, acetolactate synthase, as their mode of action. These herbicides seem to bind to an evolutionary vestige of a quinone-binding site, extraneous to the active site, that is present due to the evolutionary history of this enzyme. Besides their herbicidal effect on sensitive plants, these compounds can effect stasis in the growth of bacteria and yeast. Recently is has been reported that an experimental herbicide from Hoechst. Hoe 704. that was discovered by conventional screening techniques, inhibits the second common enzyme of branched-chain amino acid bio- synthesis [Schultz etal., FEBS Lett. 238, 375-378 (1988)]. We have also recently designed novel reaction-intermediate analogs (e.g. N-isopropyl oxalylhydroxamate) that arc exceptionally potent (Ki = 22 pM: half-time for release approximately six days) and selective inhibitors of the second common enzyme, ketol-acid reductoisomerase. Both of these selective inhibitors of the second common enzyme will kill sensitive plants, but will only inhibit the growth (without killing) of bacteria. The effects in bacteria parallel those obtained by mutations in the relevant genes, where loss of either the first or second common enzyme in the pathway gives an organ- ism that is auxotrophic for branched-chain amino acids, but does not result in a conditionally lethal phenotype. Higher plant mutants have only been obtained to date that arc deficient in functional leucine-specific gene products (as yet uncharacterized), threonine deaminase (isoleucine specific), and dihydroxyacid dehydratase (common). The phenotypes of these mutants. at least at the level of cell culture, are similar to those of their bacterial counterparts, in that auxotrophy, but not conditional lethality, is obtained. These results highlight the potential non-equality of the enzymes of branched-chain amino acid biosynthesis as targets in herbicide design.

scholarly journals Amino Acid Metabolism of Thermoanaerobacter Strain AK90: The Role of Electron-Scavenging Systems in End Product Formation

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Sean Michael Scully ◽  
Johann Orlygsson
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Amino Acid ◽  
Electron Acceptor ◽  
Detailed Examination ◽  
Product Formation ◽  
Isoleucine Leucine ◽  
Branched Chain Amino Acid ◽  
Branched Chain

The catabolism of the 20 amino acids by Thermoanaerobacter strain AK90 (KR007667) was investigated under three different conditions: as single amino acids without an electron-scavenging system, in the presence of thiosulfate, and in coculture with a hydrogenotrophic methanogen. The strain degraded only serine without an alternative electron acceptor but degraded 11 amino acids (alanine, cysteine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tyrosine, and valine) under both of the electron-scavenging systems investigated. Acetate was the dominant end product from alanine, cysteine, lysine, serine, and threonine under electron-scavenging conditions. The branched-chain amino acids, isoleucine, leucine, and valine, were degraded to their corresponding fatty acids under methanogenic conditions and to a mixture of their corresponding fatty acids and alcohols in the presence of thiosulfate. The partial pressure of hydrogen seems to be of importance for the branched-chain alcohol formation. This was suggested by low but detectable hydrogen concentrations at the end of cultivation on the branched-chain amino acid in the presence of thiosulfate but not when cocultured with the methanogen. A more detailed examination of the role of thiosulfate as an electron acceptor was performed with Thermoanaerobacter ethanolicus (DSM 2246) and Thermoanaerobacter brockii (DSM 1457).

Cryptococcus neoformans Ilv2p confers resistance to sulfometuron methyl and is required for survival at 37 °C and in vivo

Microbiology ◽  
2004 ◽  
Vol 150 (5) ◽  
pp. 1547-1558 ◽  
Author(s):  
Joanne M. Kingsbury ◽  
Zhonghui Yang ◽  
Tonya M. Ganous ◽  
Gary M. Cox ◽  
John H. McCusker
Keyword(s):  
Amino Acid ◽  
Cryptococcus Neoformans ◽  
Acetolactate Synthase ◽  
Gene Encoding ◽  
Sulfometuron Methyl ◽  
Branched Chain Amino Acid ◽  
Valine Biosynthesis ◽  
Branched Chain ◽  
Synthase Inhibitor

Acetolactate synthase catalyses the first common step in isoleucine and valine biosynthesis and is the target of several classes of inhibitors. The Cryptococcus neoformans ILV2 gene, encoding acetolactate synthase, was identified by complementation of a Saccharomyces cerevisiae ilv2 mutant. C. neoformans is highly resistant to the commercially available acetolactate synthase inhibitor, sulfometuron methyl (SM). Expression of C. neoformans ILV2 in S. cerevisiae conferred SM resistance, indicating that the SM resistance of C. neoformans is due, at least in part, to C. neoformans Ilv2p. The C. neoformans ILV2 gene was disrupted. The ilv2 mutants were auxotrophic for isoleucine and valine and the auxotrophy was satisfied by these amino acids only when proline, and not ammonium, was the nitrogen source, indicating nitrogen regulation of amino acid transport. ilv2 mutants rapidly lost viability at 37 °C and when starved for isoleucine and valine. Consistent with these phenotypes, an ilv2 mutant was avirulent and unable to survive in mice. Because C. neoformans Ilv2p is required for virulence and survival in vivo, inhibitors of branched-chain amino acid biosynthesis may make valuable antifungal agents.

scholarly journals BrnQ-type Branched-chain Amino Acid Transporters Influence Bacillus anthracis Growth and Virulence

2021 ◽  
Author(s):  
Soumita Dutta ◽  
Ileana D Corsi ◽  
Naomi Bier ◽  
Theresa M Koehler
Keyword(s):  
Amino Acid ◽  
Bacillus Anthracis ◽  
Murine Model ◽  
Amino Acid Transporters ◽  
Dependent Manner ◽  
Isoleucine Leucine ◽  
Virulence Gene Expression ◽  
Branched Chain Amino Acid ◽  
Branched Chain

Bacillus anthracis, the anthrax agent, exhibits robust proliferation in diverse niches of mammalian hosts. Metabolic attributes of B. anthracis that permit rapid growth in multiple mammalian tissues have not been established. We posit that branched-chain amino acid (BCAA: Isoleucine, leucine and valine) metabolism is key to B. anthracis pathogenesis. Increasing evidence indicates relationships between B. anthracis virulence and expression of BCAA-related genes. Expression of some BCAA-related genes is altered during culture in bovine blood in vitro and the bacterium exhibits valine auxotrophy in a blood serum mimic medium. Transcriptome analyses have revealed that the virulence regulator AtxA, that positively affects expression of the anthrax toxin and capsule genes, negatively regulates genes predicted to be associated with BCAA biosynthesis and transport. Here, we show that B. anthracis growth in defined media is severely restricted in the absence of exogenous BCAAs, indicating that BCAA transport is required for optimal growth in vitro. We demonstrate functional redundancy among multiple BrnQ-type BCAA transporters. Three transporters are associated with isoleucine and valine transport, and deletion of one, BrnQ3, attenuates virulence in a murine model for anthrax. Interestingly, an ilvD-null mutant lacking dihydroxy-acid dehydratase, an enzyme essential for BCAAs synthesis, exhibits unperturbed growth when cultured in media containing BCAAs, but is highly attenuated in the murine model. Finally, our data show that BCAAs enhance AtxA activity in a dose-dependent manner, suggesting a model in which BCAAs serve as a signal for virulence gene expression.

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