scholarly journals Precursors of the pyrimidine moiety of thiamine

1968 ◽  
Vol 106 (1) ◽  
pp. 271-277 ◽  
Author(s):  
P. C. Newell ◽  
R G Tucker
Keyword(s):  
Amino Acid ◽  
Salmonella Typhimurium ◽  
Specific Radioactivity ◽  
Cell Suspensions ◽  
Pure Form ◽  
Washed Cell ◽  
Pyrimidine Moiety

1. A method was devised for obtaining the pyrimidine moiety of thiamine in a pure form after its excretion into the medium by de-repressed washed-cell suspensions of mutants of Salmonella typhimurium LT2. 2. By using amino acid-requiring mutants, this excretion of pyrimidine moiety was shown to be dependent on the presence of both methionine and glycine. 3. In the presence of either [Me−14C]methionine or [G−14C]methionine, methionine-requiring mutants did not incorporate radioactivity into the pyrimidine moiety. 4. In contrast, both [1−14C]glycine and [2−14C]glycine were incorporated into the pyrimidine moiety excreted by glycine-requiring mutants, and this occurred with little or no dilution of specific radioactivity. 5. The possible requirement for methionine as a cofactor and the significance of the incorporation of both carbon atoms of glycine are discussed.

scholarly journals Biosynthesis of the pyrimidine moiety of thiamine. A new route of pyrimidine biosynthesis involving purine intermediates

1968 ◽  
Vol 106 (1) ◽  
pp. 279-287 ◽  
Author(s):  
P. C. Newell ◽  
R G Tucker
Keyword(s):  
Salmonella Typhimurium ◽  
Specific Radioactivity ◽  
Pyrimidine Biosynthesis ◽  
Biosynthetic Pathways ◽  
Purine Pathway ◽  
Growth Requirement ◽  
Pyrimidine Moiety

1. The pattern of distribution on the purine pathway of mutants of Salmonella typhimurium LT2 that had the double growth requirement for a purine plus the pyrimidine moiety of thiamine (ath mutants) indicated that purines and the pyrimidine moiety of thiamine share the early part of their biosynthetic pathways, and that 4-aminoimidazole ribonucleotide (AIR) is the last common intermediate. Two mutants that at first appeared anomalous were further investigated and found not to affect this deduction. 2. The ribonucleoside form of AIR (AIRs) satisfied the requirements both for a purine and for the pyrimidine moiety of thiamine of an ath mutant. 3. Methionine was required for the conversion of AIR into the pyrimidine moiety. 4. Radioactive AIRs was converted into radioactive pyrimidine moiety by an ath mutant without significant dilution of specific radioactivity. 5. Possible mechanisms for pyrimidine-moiety biosynthesis from AIR are discussed.

How Optimized Is the Translational Machinery in Escherichia coli, Salmonella typhimurium and Saccharomyces cerevisiae?

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Xuhua Xia
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Salmonella Typhimurium ◽  
Codon Usage ◽  
Translational Efficiency ◽  
Square Root ◽  
Translational Machinery ◽  
Mutual Adaptation ◽  
Trna Species

Abstract The optimization of the translational machinery in cells requires the mutual adaptation of codon usage and tRNA concentration, and the adaptation of tRNA concentration to amino acid usage. Two predictions were derived based on a simple deterministic model of translation which assumes that elongation of the peptide chain is rate-limiting. The highest translational efficiency is achieved when the codon recognized by the most abundant tRNA reaches the maximum frequency. For each codon family, the tRNA concentration is optimally adapted to codon usage when the concentration of different tRNA species matches the square-root of the frequency of their corresponding synonymous codons. When tRNA concentration and codon usage are well adapted to each other, the optimal content of all tRNA species carrying the same amino acid should match the square-root of the frequency of the amino acid. These predictions are examined against empirical data from Escherichia coli, Salmonella typhimurium, and Saccharomyces cerevisiae.

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