Transcription of the tryptophan operon in polarity mutants of Escherichia coli. I. Characterization of the tryptophan messenger RNA of polar mutants.

摘要: Amber, ochre, and frame-shift polarity mutants of the tryptophan operon Escherichia coli were examined in transcription studies to determine whether translational was associated with an alteration tryp -mRNA population. Tryp isolated from bacterial cultures following a shift repression derepression conditions. The pulse-labeled [ 3 H]uridine at some period soon after initiation derepression. Total regions corresponding different segments measured by hybridizing DNA o80 transducing phages carrying operon. It found that strong generally contained less total than identically treated wild-type strain or missense mutant. This result most evident alterations E gene, but data obtained are suggestive for other genes Specific hybridization demonstrated deficient mRNA on operator-distal side mutated gene. In agreement this finding, sucrose gradient sedimentation profiles indicated majority molecules each mutant smaller normal. also shown size predominant species increased relation genetic distance beginning first gene site mutation. Estimates relative numbers normal length smaller-than-normal weak gave values consistent conclusion extent any approximates representation