Proofreading in vivo: Editing of homocysteine by methionyl-tRNA synthetase in Escherichia coli
- Univ. of Medicine and Dentistry of New Jersey, Newark (USA)
Previous in vitro studies have established a pre-transfer proofreading mechanism for editing of homocysteine by bacterial methionyl-, isoleucyl-, and valyl-tRNA synthetases. The unusual feature of the editing is the formation of a distinct compound, homocysteine thiolactone. Now, two-dimensional TLC analysis of 35S-labeled amino acids extracted from cultures of the bacterium Escherichia coli reveals that the thiolactone is also synthesized in vivo. In E. coli, the thiolactone is made from homocysteine in a reaction catalyzed by methionyl-tRNA synthetase. One molecule of homocysteine is edited as thiolactone per 109 molecules of methionine incorporated into protein in vivo. These results not only directly demonstrate that the adenylate proofreading pathway for rejection of misactivated homocysteine operates in vivo in E. coli but, in general, establish the importance of error-editing mechanisms in living cells.
- OSTI ID:
- 6709044
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 87:12; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HOMOCYSTEINE
BIOLOGICAL PATHWAYS
HYDROLASES
BIOCHEMICAL REACTION KINETICS
LACTONES
BIOSYNTHESIS
AMINO ACIDS
ESCHERICHIA COLI
PLASMIDS
SULFUR 35
THIN-LAYER CHROMATOGRAPHY
TRACER TECHNIQUES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
ENZYMES
ESTERS
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SEPARATION PROCESSES
SULFUR ISOTOPES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques