JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jensen, K F
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Jensen, K F
J Bacteriol. 1993 June; 175(11): 3401-3407

research-article

The Escherichia coli K-12 "wild types" W3110 and MG1655 have an rph frameshift mutation that leads to pyrimidine starvation due to low pyrE expression levels.

K F Jensen

Institute of Biological Chemistry, University of Copenhagen, Denmark.

ABSTRACT

The widely used and closely related Escherichia coli "wild types" W3110 and MG1655, as well as their common ancestor W1485, starve for pyrimidine in minimal medium because of a suboptimal content of orotate phosphoribosyltransferase, which is encoded by the pyrE gene. This conclusion was based on the findings that (i) the strains grew 10 to 15% more slowly in pyrimidine-free medium than in medium containing uracil; (ii) their levels of aspartate transcarbamylase were highly derepressed, as is characteristic for pyrimidine starvation conditions; and (iii) their levels of orotate phosphoribosyltransferase were low. After introduction of a plasmid carrying the rph-pyrE operon from strain HfrH, the growth rates were no longer stimulated by uracil and the levels of aspartate transcarbamylase were low and similar to the levels observed for other strains of E. coli K-12, E. coli B, and Salmonella typhimurium. To identify the mutation responsible for these phenotypes, the rph-pyrE operon of W3110 was cloned in pBR322 from Kohara bacteriophage lambda 2A6. DNA sequencing revealed that a GC base pair was missing near the end of the rph gene of W3110. This one-base-pair deletion results in a frame shift of translation over the last 15 codons and reduces the size of the rph gene product by 10 amino acid residues relative to the size of RNase PH of other E. coli strains, as confirmed by analysis of protein synthesis in minicells. The truncated protein lacks RNase PH activity, and the premature translation stop in the rph cistron explains the low levels of orotate phosphoribosyltransferase in W3110, since close coupling between transcription and translation is needed to support optimal levels of transcription past the intercistronic pyrE attenuator.

J Bacteriol. 1993 June; 175(11): 3401-3407




This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 1993 by the American Society for Microbiology. All rights reserved.