Organization and functions of genes in the upstream region of tyrT of Escherichia coli: phenotypes of mutants with partial deletion of a new gene (tgs)

Abstract

A AiyrT::kan mutant from Escherichia coli K-12 (DTK-12) shows a transient growth lag that is caused by glycine starvation (U. Michelsen, M. Bosl, T. Dingermann, and H. Kersten, J. Bacteriol. 171:5987-5994, 1989).The same deletion, transduced into the relA spoTi mutant CA274 to construct strain DTC274, caused complete growth inhibition in glucose minimal medium. Here, we show that the tyrT 5' region contains three new open reading frames in the order 0RF37-->0RF34-*0RF32-*tyrT and that the AtyrT::kan allele used previously deletes tyrT as well as a carboxy-terminal portion of 0RF32. A plasmid encoding 0RF32 totally complemented the inability of strain DTC274 to grow on glucose minimal medium as well as the transient glycine starvation phenomenon in DTK-12, and 0RF32 was designated tgs. Partial deletion oftgs, cotransduced with the marker AlyrT::kan, was responsible for the completely different phenotypes of the deletion mutants DTK-12 and DTC274. The deduced Tgs protein sequence showed significant homology to the PurN protein of E. coli and to enzymes with glycinamide ribonucleotide transformylase activity. We discuss whether growth inhibition in strain DTC274 may be caused by synergistic effects with the preexisting mutations relA1 and spoT). The deduced protein sequence of ORF37 showed striking similarity to regulator response proteins and is probably a new member of this family. A spontaneous mutation in ORF37, caused by the integration of an insertion element, IS], exhibited no phenotype.Tyrosine-accepting tRNA is encoded by two genes in Escherichia coli, tyrT and tyrU. The tyrT operon and its regulation have been well investigated: it is under stringent control (17) and under growth rate control (40). An upstream activation sequence, including a binding site for the transactivator protein Fis (25), permits an optimal rate of transcription (16,39).The most striking feature of the tyrT operon is its structural arrangement (9,20,29,30 In a further study, this RNA, designated rtT RNA, has been identified nd characterized (3). We have made two unexpected ob ervations. (i) Plasmid-expressed rtT RNA is not only invol ed in complementation of the glycine starvation in the AtyrT:: an strain DTK-12 but also influences growth arrest induced b isoleucine deprivation. Therefore, a general modulatory ro e of rtT RNA upon stringent control that is not restricted to glycine starvation in strain has been suggested. (ii) The extent of growth delay in the AtyrT::kan strain DTK-12 is increased under more-limiting conditions with glycerol as carbon source. Under these conditions, the characteristic lag phase in strain DTK-12 has been only partially o ercome by the tyrT operon, probably because of the modulato effect of rtT RNA upon stringent control, indicating that de etion of the tyrT operon is not or at least is not the only genetic cause for the phenomenon of transient glycine starvation, designated the tyrT deletion phenotype (22).In the stl dy presented here, the hypothesis that a second site mutation i involved in genera...

The response regulator SprE controls the stability of RpoS.

“…Since rpoS affects ompF transcription in a stationary-phase-specific fashion, components of the rpoS pathway should likewise have a stationary-phase-specific effect on ompF. As indicated by 3-galactosidase assays on strains harboring 4(ompF'-lacZ+) 16 30). In light of this gene's involvement in the regulation of rpoS, we have named it sprE (stationary-phase regulator).…”

“…The resulting PCR product was used as a template for DNA sequence analysis as described (28) with a few minor modifications (29). The insertion joint was found to be 27 bp upstream of the translational start site of ORF37 (30). The transposon sequence appeared to have been rearranged; the details of this aberrant insertion/rearrangement are unknown.…”

The Response Regulator SprE (RssB) Modulates Polyadenylation and mRNA Stability inEscherichia coli

“…The N-terminal domain of SprE shares strong sequence homology with the receiver domain of the response regulator family of proteins (5). In a typical two domain response regulator, regulation of activity occurs through phosphorylation at a conserved aspartate (D58 in SprE) in the N-terminal domain.…”

RpoS-Dependent Transcriptional Control of sprE : Regulatory Feedback Loop

“…Although those studies did not prove the exact location of the sprE promoter, their reporter fusion data showed that sprE transcription can occur independently from that of its upstream gene, rssA (11). Prior to these studies it was assumed, based on DNA sequence analysis, that rssA and sprE constitute an operon (5,22). In addition, RssA itself was implicated in the SprE pathway regulating RpoS, although its function has never been clearly demonstrated (unpublished results cited in references 13 and 22).…”