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.

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.

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).

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.

scholarly journals Mutants affecting amino acid cross-pathway control inNeurospora crassa

1982 ◽  
Vol 39 (2) ◽  
pp. 169-185 ◽  
Author(s):  
Ilse B. Barthelmess
Keyword(s):  
Amino Acid ◽  
Neurospora Crassa ◽  
Enzyme Concentration ◽  
Amino Acid Biosynthesis ◽  
Lysine Biosynthesis ◽  
Biosynthetic Enzymes ◽  
Wild Type ◽  
Acid Biosynthesis ◽  
The Cross ◽  
Inneurospora Crassa

SummaryArginine-requiring mutants ofNeurospora crassawere isolated using a strain partially impaired in an enzyme of the arginine pathway (bradytroph). Among these, five strains were found which carry mutations at a new locus,cpc-1+. The recessivecpc-1alleles interfere with the cross-pathway control of amino acid biosynthetic enzymes. The enzymes studied, three of arginine and one each of histidine and lysine biosynthesis, fail to derepress under conditions which normally result in elevation of enzyme concentration, namely arginine, histidine or tryptophan limitation. Enzymes not involved in amino acid biosynthesis are still able to derepress in the presence ofcpc-1. In wild-type backgound, i.e. with the bradytroph replaced,cpc-1strains lose the original arginine-requirement.cpc-1mutations confer sensitivity of growth to 3-amino-1,2,4-triazole.

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