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The cis ‐effect of a nascent peptide on its translating ribosome: influence of the cat‐86 leader pentapeptide on translation termination at leader codon 6
Author(s) -
Rogers Elizabeth J.,
Lovett Paul S.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb01007.x
Subject(s) - pentapeptide repeat , biology , ribosome , ribosomal binding site , shine dalgarno sequence , translation (biology) , start codon , a site , protein biosynthesis , p site , peptide , stop codon , peptidyl transferase , biochemistry , genetics , amino acid , gene , messenger rna , binding site , rna
Summary Inducible cat genes from Gram‐positive bacteria are regulated by translation attenuation. The inducer chloramphenicol stalls a ribosome at a specific site in the leader of cat transcripts; this destabillzes a downstream stem‐loop structure that normally sequesters the ribosome‐binding site for the cat structural gene. The five‐amino‐acid peptide MVKTD that is synthesized when a ribosome has translated to the leader induction site is an inhibitor of peptidyl transferase In vitro. Thus, the peptide may be the in vivo determinant of the site of ribosome stalling. Here we provide evidence that the leader pentapeptide can exert a cis ‐effect on its translating ribosome In vivo. Converting leader codon 6 to the ochre codon results in expression of cat‐86 in the absence of Inducer. We term this autoinduction. Autoinduction is abolished by mutations that change the amino‐acid sequence of the leader peptide but have no, or little, effect on the sequence of nucleotides at the leader stall site. In contrast, four nucleotide changes within the leader site occupied by the stalled ribosome that result in synonymous codon replacements do not diminish autoinduction. Our evidence indicates that the cat‐86 leader pentapeptide can alter the function of its translating ribosome.