Superattenuation in the tryptophan operon of Serratia marcescens

Deletions were generated in vitro in the leader region of the tryptophan operon of Serratia marcescens and subsequently incorporated into the Escherichia coli chromosome in single copy form. Deletions which removed the translation start codon for the leader peptide or which ended in the ribosome recognition region preceding the leader peptide coding segment, caused super attenuation, that is, increased transcription termination at the attenuator. Apparently, the capacity to initiate translation of this coding region modulates expression of the operon.