Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1995 Dec;177(24):7245-54.
doi: 10.1128/jb.177.24.7245-7254.1995.

Evidence suggesting cis action by the TnaC leader peptide in regulating transcription attenuation in the tryptophanase operon of Escherichia coli

K Gish  1 , C Yanofsky
Affiliations

Evidence suggesting cis action by the TnaC leader peptide in regulating transcription attenuation in the tryptophanase operon of Escherichia coli

K Gish et al. J Bacteriol. 1995 Dec.

Abstract

Expression of the tryptophanase (tna) operon in Escherichia coli is regulated by catabolite repression and transcription attenuation. Elevated levels of tryptophan induce transcription antitermination at one or more Rho factor-dependent termination sites in the leader region of the operon. Induction requires translation of a 24-residue coding region, tnaC, located in the 319-nucleotide transcribed leader region preceding tnaA, the structural gene for tryptophanase. In the present paper, we show that two bacterial species that lack tryptophanase activity, Enterobacter aerogenes and Salmonella typhimurium, allow tryptophanase induction and tna operon regulation when they carry a plasmid containing the E. coli tna operon. The role of tnaC in induction was examined by introducing mutations in a 24-nucleotide segment of tnaC of E. coli surrounding and including the crucial Trp codon 12. Some mutations resulted in a noninducible phenotype; these mostly introduced nonconservative amino acid substitutions in TnaC. Other mutations had little or no effect; these generally were in third positions of codons or introduced conservative amino acid replacements. A tryptophan-inserting, UGA-reading glutamine suppressor tRNA was observed to restore partial regulation when Trp codon 12 of tnaC was changed to UGA. Stop codons introduced downstream of Trp codon 12 in all three reading frames established that induction requires translation in the natural tnaC reading frame. Our findings suggest that the TnaC leader peptide acts in cis to prevent Rho-dependent termination.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Science. 1988 Feb 26;239(4843):1005-12 - PubMed
    1. J Bacteriol. 1963 Jan;85:245-6 - PubMed
    1. Proc Natl Acad Sci U S A. 1990 Jun;87(12):4660-4 - PubMed
    1. J Biol Chem. 1988 Jan 15;263(2):609-12 - PubMed
    1. J Bacteriol. 1986 Jul;167(1):383-6 - PubMed

Publication types

LinkOut - more resources