Chlorismic acid, a key metabolite in modification of tRNA. [Escherichia coli]
- Umea Univ., Umea (Sweden)
- Univ. of Utah, Salt Lake City (USA)
Chorismic acid is the common precursor for the biosynthesis of the three aromatic amino acids as well as for four vitamins. Mutants of Escherichia coli defective in any of the genes involved in the synthesis of chorismic acid are also unable to synthesize uridine 5-oxyacetic acid (cmo{sup 5}U) and its methyl ester (mcmo{sup 5}U). Both modified nucleosides are normally present in the wobble position of some tRNA species. Mutants defective in any of the specific pathways leading to phenylalanine, tyrosine, tryptophan, folate, enterochelin, ubiquinone, and menaquinone have normal levels of cmo{sup 5}U and mcmo{sup 5}U in their tRNA. The presence of shikimic acid in the growth medium restores the ability of an aroD mutant to synthesize cmo{sup 5}U, while O-succinylbenzoate, which is an early intermediate in the synthesis of menaquinone, does not. This, chorismic acid is a key metabolite in the synthesis of these tow modified nucleosides in tRNA. The absence of chorismic acid blocks the formation of cmo{sup 5}U and mcmo{sup 5}U at the first step, which might be the formation of 5-hydroxyuridine. This results in an unmodified U in the wobble position of tRNA{sub 1}{sup Val} and in most of the tRNAs normally containing cmo{sup 5}U and mcmo{sup 5}U. Since cmo{sup 5}U and mcmo{sup 5}U are synthesized under anaerobic conditions, the formation of these nucleosides does not require molecular oxygen. One of the carbon atoms of the side chain, O-CH{sub 2}-COOH, originates from the methyl group of methionine. The other carbon atom does not originate directly from the C-1 pool, from the carboxyl group of methionine, or from bicarbonate.
- OSTI ID:
- 7016642
- Journal Information:
- Journal of Bacteriology; (USA), Vol. 172:1; ISSN 0021-9193
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ESCHERICHIA COLI
METABOLISM
NUCLEOSIDES
BIOCHEMICAL REACTION KINETICS
AMINO ACIDS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
METABOLITES
MUTANTS
TRANSFER RNA
BACTERIA
CARBOXYLIC ACIDS
KINETICS
MICROORGANISMS
NUCLEIC ACIDS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
REACTION KINETICS
RIBOSIDES
RNA
SYNTHESIS
550200* - Biochemistry