Isolation and characterization of mutations creating high-efficiency transcription initiation signals within the trp operon of Escherichia coli.
Abstract
Isolation and characterization of mutations creating high-efficiency transcription initiation signals within the trp operon of Escherichia coli. A McPartland and R L Somerville ABSTRACT Two different mutational events generate promoter-active deoxyribonucleic acid sequences within the trp operon of Escherichia coli, probably through single base-pair changes. The mutations, obtained after ethyl methane sulfonate mutagenesis by selecting for elevated lac gene expression in a trp-lac fusion, are cis dominant and trans recessive with respect to their effects on the synthesis of downstream enzymes. One of the mutants (trpD11), obtained repeatedly under the selective conditions employed, prevents the formation of active phosphoribosyltransferase. The second mutation, trp3B, has no effects on any trp enzyme. By deletion mapping, trpD11 was localized near the operator-distal end of trpD, outside the segment of deoxyribonucleic acid that contains the low-efficiency internal promoter trpP2. Reversion to prototrophy of trpD11 was greatly stimulated by 2-aminopurine and ethyl methane sulfonate. Tests with suppressors indicated that trpD11 is a UAA (ochre) nonsense mutation. Under repression conditions, strains harboring either lesion in a normal trp operon synthesize the tryptophan biosynthetic enzymes in a noncoordinate fashion. The products of the operator-distal structural genes trpC, trpB, and trpA are formed at rates approximately 15-fold higher than those of wild type. The enzymes encoded by operator-proximal genes trpE and trpD are low or not detectable. Under derepression conditions, coordinate expression of the operon was observed. CiteULike Connotea Delicious Digg Facebook Google+ Mendeley Reddit StumbleUpon Twitter What's this? « Previous | Next Article » Table of Contents This Article J. Bacteriol. November 1976 vol. 128 no. 2 557-572 » Abstract PDF Classifications Research Article Services Email this article to a colleague Similar articles in ASM journals Alert me when this article is cited Alert me if a correction is posted Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of JB Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Load citing article information Citing articles via Web of Science Citing articles via Google Scholar Google Scholar Articles by McPartland, A. Articles by Somerville, R. L. Search for related content PubMed PubMed citation Articles by McPartland, A. Articles by Somerville, R. L. Related Content Load related web page information Social Bookmarking CiteULike Connotea Delicious Digg Facebook Google+ Mendeley Reddit StumbleUpon Twitter What's this? current issue January 2012, volume 194, issue 1 Alert me to new issues of JB About JB Subscribers Authors Reviewers Advertisers Inquiries from the Press Permissions & Commercial Reprints ASM Journals Public Access Policy JB RSS Feeds 1752 N Street N.W. • Washington DC 20036 202.737.3600 • 202.942.9355 fax • journals@asmusa.org Print ISSN: 0021-9193 Online ISSN: 1098-5530 Copyright © 2011 by the American Society for Microbiology. For an alternate route to JB .asm.org, visit: http://intl- JB .asm.org | More Info» var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); var pageTracker = _gat._getTracker("UA-5821458-9"); pageTracker._trackPageview();