Abundant urinary amino acids activate glutamine synthetase-encoding glnA by two different mechanisms in Escherichia coli

• Published in: Journal of bacteriology Vol. 206; no. 3; p. e0037623
• Main Authors: Urs, Karthik, Zimmern, Philippe E, Reitzer, Larry
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 21.03.2024
• Subjects: Amino acids; Ammonia; E coli; Enzyme kinetics; Escherichia coli; Gene expression; Genetics and Molecular Biology; Glutamate-ammonia ligase; Glutamine; Immunoassay; Metabolism; Promoters; Research Article; Reverse transcription; Urea; Ureas; Urinary tract infections; Urine; urine composition; glutamine synthetase; Escherichia coli; urinary tract infections
• ISSN: 0021-9193; 1098-5530; 1098-5530
• DOI: 10.1128/jb.00376-23

Growth of uropathogenic in the bladder induces transcription of which codes for the ammonia-assimilating glutamine synthetase (GS) despite the normally suppressive high ammonia concentration. We previously showed that the major urinary component, urea, induces transcription from the Crp-dependent promoter, but the urea-induced transcript is not translated. Our purpose here was to determine whether the most abundant urinary amino acids, which are known to inhibit GS activity , also affect transcription . We found that the abundant amino acids impaired growth, which glutamine and glutamate reversed; this implies inhibition of GS activity. In strains with deletions of and that force transcription from the and promoters, respectively, we examined growth and transcription with a transcriptional fusion and quantitative reverse transcription PCR with primers that can distinguish transcription from the two promoters. The abundant urinary amino acids stimulated transcription from the promoter in the absence of urea but from the promoter in the presence of urea. However, transcription from did not produce a translatable mRNA or GS as assessed by a translational fusion, enzymatic assay of GS, and Western blot to detect GS antigen in urea-containing media. We discuss these results within the context of the extremely rapid growth of uropathogenic in urine, the different factors that control the two promoters and possible mechanisms that either overcome or bypass the urea-imposed block of glutamine synthesis during bacterial growth in urine.IMPORTANCEKnowledge of the regulatory mechanisms for genes expressed at the site of infection provides insight into the virulence of pathogenic bacteria. During urinary tract infections-most often caused by -growth in urine induces the gene which codes for glutamine synthetase. The most abundant urinary amino acids amplified the effect of urea which resulted in hypertranscription from the promoter and, unexpectedly, an untranslated transcript. must overcome this block in glutamine synthesis during growth in urine, and the mechanism of glutamine acquisition or synthesis may suggest a possible therapy.