Rho-dependent transcription termination in the tryptophanase operon leader region of Escherichia coli K-12

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Abstract
Recent studies have suggested that expression of the tryptophanase (tna) operon of Escherichia coli is subject to transcription termination-antitermination control (V. Stewart and C. Yanofsky, J. Bacteriol. 164:731-740, 1985). In vivo studies have indicated that the transcribed leader region, tnaL, contains a site or sites of rho-dependent transcription termination (rho is the polypeptide product of the gene rho). We now report direct in vitro evidence that tnaL contains rho-dependent termination sites. In vivo termination appeared to occur at the rho-dependent termination sites identified in vitro. Transcription pausing analyses correlated sites of pausing in tnaL with sites of rho-dependent termination.