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The tryptophan repressor sequence is highly conserved among the Enterobacteriaceae
D N Arvidson1, C G Arvidson, C L Lawson
1California Institute of Biological Research, La Jolla 92037.
Nucleic Acids Research
|May 25, 1994
Summary
Researchers cloned tryptophan repressor (TrpR) genes from Enterobacter species into E. coli. Sequence analysis revealed conserved interactions crucial for regulating tryptophan biosynthesis, despite minor sequence variations.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Tryptophan biosynthesis in E. coli is regulated by the TrpR protein, which forms a complex with L-tryptophan to inhibit gene transcription.
- The trp operator sequences are conserved among enteric bacteria, suggesting cross-species gene function.
Purpose of the Study:
- To clone and characterize homologous trpR genes from other bacterial species.
- To investigate the structural and functional conservation of TrpR proteins in enteric bacteria.
Main Methods:
- Site-directed mutagenesis was used to create a trpR deletion (delta trpR504) in E. coli.
- Complementation cloning was employed to isolate trpR homologues from Enterobacter aerogenes and Enterobacter cloacae.
- Beta-galactosidase activity from a trpE-lacZ gene fusion was used to score complementation.
Main Results:
- TRpR genes from E. aerogenes and E. cloacae were successfully cloned by complementation.
- Predicted amino acid sequences of enteric TrpR proteins showed variations clustered away from DNA-binding domains.
- These variations are predicted to have minimal impact on repressor-DNA or repressor-repressor interactions.
Conclusions:
- Homologous trpR genes from enteric bacteria can functionally complement E. coli trpR deletions.
- The TrpR protein structure and function are conserved among enteric Gram-negative bacteria.
- Phylogenetic analysis of TrpR sequences supports evolutionary relationships within this bacterial group.