Homoserine kinase and threonine synthase in methionine-overproducing soybean tissue cultures

1988 ◽  
Vol 7 (7) ◽  
pp. 477-480 ◽  
Author(s):  
Jonathan M. Greenberg ◽  
John F. Thompson ◽  
James T. Madison
Keyword(s):  
Tissue Cultures ◽  
Threonine Synthase ◽  
Homoserine Kinase ◽  
Soybean Tissue

The sensitivity of soybean tissue cultures to the thymidine analogue, 5-bromodeoxyuridine

1979 ◽  
Vol 17 (1) ◽  
pp. 123-128 ◽  
Author(s):  
T.L. Wang
Keyword(s):  
Tissue Cultures ◽  
Thymidine Analogue ◽  
Soybean Tissue

scholarly journals The expression of Escherichia coli threonine synthase and the production of threonine from homoserine in mouse 3T3 cells

1993 ◽  
Vol 291 (1) ◽  
pp. 315-322 ◽  
Author(s):  
W D Rees ◽  
S M Hay
Keyword(s):  
Escherichia Coli ◽  
Protein A ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Eukaryotic Expression ◽  
Cell Protein ◽  
3T3 Cells ◽  
Threonine Synthase ◽  
Homoserine Kinase ◽  
A Cell

We have subcloned the coding sequence for the Escherichia coli threonine synthase gene into a eukaryotic expression vector based on the simian-virus-40 early promoter. When mouse 3T3 cells which already expressed homoserine kinase were transfected with the new plasmid, the cells were able to incorporate radioactivity from [14C]homoserine into their cell proteins. Stable cell lines were established by co-transfecting 3T3 cells with the plasmid coding for threonine synthase and another coding for homoserine kinase and G-418 (Geneticin) resistance. Cells were selected for G-418 resistance and then screened for an ability to synthesize threonine from homoserine and incorporate it into the cell protein. A cell line which expressed both the homoserine kinase and threonine synthase genes was capable of growth in a threonine-deficient medium containing homoserine.

scholarly journals Phospholipid Turnover in Soybean Tissue Cultures

1977 ◽  
Vol 60 (5) ◽  
pp. 754-758 ◽  
Author(s):  
Thomas S. Moore
Keyword(s):  
Tissue Cultures ◽  
Phospholipid Turnover ◽  
Soybean Tissue

scholarly journals Homoserine Toxicity in Saccharomyces cerevisiae and Candida albicans Homoserine Kinase (thr1Δ) Mutants

2010 ◽  
Vol 9 (5) ◽  
pp. 717-728 ◽  
Author(s):  
Joanne M. Kingsbury ◽  
John H. McCusker
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Candida Albicans ◽  
Biosynthetic Genes ◽  
Ubiquitin Pathway ◽  
Content Type ◽  
Threonine Synthase ◽  
Copy Numbers ◽  
Homoserine Kinase

ABSTRACT In addition to threonine auxotrophy, mutation of the Saccharomyces cerevisiae threonine biosynthetic genes THR1 (encoding homoserine kinase) and THR4 (encoding threonine synthase) results in a plethora of other phenotypes. We investigated the basis for these other phenotypes and found that they are dependent on the toxic biosynthetic intermediate homoserine. Moreover, homoserine is also toxic for Candida albicans thr1Δ mutants. Since increasing levels of threonine, but not other amino acids, overcome the homoserine toxicity of thr1Δ mutants, homoserine may act as a toxic threonine analog. Homoserine-mediated lethality of thr1Δ mutants is blocked by cycloheximide, consistent with a role for protein synthesis in this lethality. We identified various proteasome and ubiquitin pathway components that either when mutated or present in high copy numbers suppressed the thr1Δ mutant homoserine toxicity. Since the doa4Δ and proteasome mutants identified have reduced ubiquitin- and/or proteasome-mediated proteolysis, the degradation of a particular protein or subset of proteins likely contributes to homoserine toxicity.

Role of homoserine and threonine pathway intermediates as precursors for the biosynthesis of aminoethoxyvinylglycine in Streptomyces sp. NRRL 5331

Microbiology ◽  
2004 ◽  
Vol 150 (5) ◽  
pp. 1467-1474 ◽  
Author(s):  
Mónica Fernández ◽  
Yolanda Cuadrado ◽  
Jesús F. Aparicio ◽  
Juan F. Martín
Keyword(s):  
Gene Disruption ◽  
Homoserine Dehydrogenase ◽  
Streptomyces Sp ◽  
Threonine Synthase ◽  
Homoserine Kinase ◽  
Negative Effect ◽  
Branching Point ◽  
Threonine Biosynthesis ◽  
Null Mutants

The genes hom, thrB and thrC, encoding homoserine dehydrogenase, homoserine kinase (HK) and threonine synthase, respectively, involved in the last steps of threonine biosynthesis, have been studied in Streptomyces sp. NRRL 5331, the producer of the ethylene synthetase inhibitor aminoethoxyvinylglycine (AVG), in order to determine their role in the biosynthesis of AVG. Different null mutants were obtained by plasmid-mediated disruption of each of the three genes. thrC gene disruption had no effect on AVG production, while the disruption of thrB blocked HK activity and substantially reduced the yield of this metabolite, probably due to the accumulation of homoserine and/or methionine which have a negative effect on AVG biosynthesis. Disruption of hom (thrA) completely blocked AVG biosynthesis, indicating that homoserine lies at the branching point of the aspartic-acid-derived biosynthetic route that leads to AVG. The four carbon atoms of the vinylglycine moiety of AVG derive, therefore, from homoserine.

scholarly journals Threonine synthesis from homoserine as a selectable marker in mammalian cells

1994 ◽  
Vol 299 (3) ◽  
pp. 637-644 ◽  
Author(s):  
W D Rees ◽  
S D Grant ◽  
S M Hay ◽  
K M Saqib
Keyword(s):  
Escherichia Coli ◽  
Active Region ◽  
Cell Lines ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Selectable Marker ◽  
Threonine Synthase ◽  
Homoserine Kinase ◽  
Mouse Cells ◽  
High Concentrations

The plasmid pSVthrBC expresses the Escherichia coli thrB (homoserine kinase) and thrC (threonine synthase) genes in mouse cells and enables them to synthesize threonine from homoserine. After transfection with pSVthrBC and culture in medium containing homoserine, only cells that have incorporated pSVthrBC survive. Homoserine at concentrations greater than 1 mM is toxic to mammalian cells. Mouse cells selected from medium containing 5 mM homoserine had incorporated 20-100 copies of the plasmid per cell and had homoserine kinase activities of 0.001-0.012 nmol/min per mg of protein per copy. Cells selected from medium containing 10 mM homoserine had incorporated one or two copies of the plasmid per cell and had homoserine kinase activities of 0.06-0.39 nmol/min per mg of protein per copy. By using high concentrations of homoserine, it is possible to use pSVthrBC to select and isolate cell lines that have one or two copies of the plasmid incorporated into an active region of chromatin. CHO and HeLa cells have also been successfully transfected with pSVthrBC. COS-7 cells are naturally resistant to homoserine as they are able to metabolize homoserine.

Influence of Osmotic Potential on the Growth and Development of Soybean Tissue Cultures 1

Crop Science ◽  
1975 ◽  
Vol 15 (6) ◽  
pp. 750-752 ◽  
Author(s):  
S. L. Kimball ◽  
W. D. Beversdorf ◽  
E. T. Bingham
Keyword(s):  
Osmotic Potential ◽  
Growth And Development ◽  
Tissue Cultures ◽  
Soybean Tissue

scholarly journals Fungal Homoserine Kinase (thr1Δ) Mutants Are Attenuated in Virulence and Die Rapidly upon Threonine Starvation and Serum Incubation

2010 ◽  
Vol 9 (5) ◽  
pp. 729-737 ◽  
Author(s):  
Joanne M. Kingsbury ◽  
John H. McCusker
Keyword(s):  
Drug Targets ◽  
Antifungal Drug ◽  
Aspartate Kinase ◽  
Biosynthetic Enzymes ◽  
Content Type ◽  
Threonine Synthase ◽  
Homoserine Kinase ◽  
Exciting Potential ◽  
Feedback Inhibitor

ABSTRACT The fungally conserved subset of amino acid biosynthetic enzymes not present in humans offer exciting potential as an unexploited class of antifungal drug targets. Since threonine biosynthesis is essential in Cryptococcus neoformans, we further explored the potential of threonine biosynthetic enzymes as antifungal drug targets by determining the survival in mice of Saccharomyces cerevisiae homoserine kinase (thr1Δ) and threonine synthase (thr4Δ) mutants. In striking contrast to aspartate kinase (hom3Δ) mutants, S. cerevisiae thr1Δ and thr4Δ mutants were severely depleted after only 4 h in vivo. Similarly, Candida albicans thr1Δ mutants, but not hom3Δ mutants, were significantly attenuated in virulence. Consistent with the in vivo phenotypes, S. cerevisiae thr1Δ and thr4Δ mutants as well as C. albicans thr1Δ mutants were extremely serum sensitive. In both species, serum sensitivity was suppressed by the addition of threonine, a feedback inhibitor of Hom3p. Because mutation of the HOM3 and HOM6 genes, required for the production of the toxic pathway intermediate homoserine, also suppressed serum sensitivity, we hypothesize that serum sensitivity is a consequence of homoserine accumulation. Serum survival is critical for dissemination, an important virulence determinant: thus, together with the essential nature of C. neoformans threonine synthesis, the cross-species serum sensitivity of thr1Δ mutants makes the fungus-specific Thr1p, and likely Thr4p, ideal antifungal drug targets.

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