The tyrT locus of Escherichia coli exhibits a regulatory function for glycine metabolism.
The tyrT locus in Escherichia coli codes for two gene copies of tRNA(1Tyr). Both genes are organized in one operon, which has a unique structure. The two tRNA genes are separated by a spacer segment highly homologous to a part of a unit which is repeated three times in the distal portion of the locus. This operon also contains coding capacity for a small basic protein. A genomic deletion of this locus was constructed and marked by a kanamycin resistance cassette. Deletion mutants exhibited a characteristic phenotype when cells were shifted from rich medium to minimal medium. The cells entered a transient lag phase, apparently resulting from specific glycine starvation. This phenotype involved stringent response and was therefore not observed in relA derivatives. The genomic deletion was complemented in trans by a plasmid-borne tyrT locus. From deletion mapping, it can be concluded that a product of the tyrT operon is responsible for complementation. However, neither the tRNA(1Tyr) nor the proposed basic protein is the complementation-competent entity.
Michelsen
U
U
Institut für Biochemie der Medizinischen Fakultät, Universität Erlangen-Nürnberg, Federal Republic of Germany.
Bösl
M
M
Dingermann
T
T
Kersten
H
H
D000596:Amino Acids / Q000378:metabolism; D015139:Blotting, Southern; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005798:Genes, Bacterial; D005809:Genes, Regulator; D005816:Genetic Complementation Test; D005838:Genotype; D005998:Glycine / Q000378:metabolism*; D009154:Mutation; D009693:Nucleic Acid Hybridization; D012345:RNA, Transfer, Amino Acid-Specific / Q000235:genetics*; D012365:RNA, Transfer, Tyr / Q000235:genetics*; D015183:Restriction Mapping
D000596:Amino Acids; D012345:RNA, Transfer, Amino Acid-Specific; D012365:RNA, Transfer, Tyr; D005998:Glycine