PMID:11844765

Citation	Pease, AJ, Roa, BR, Luo, W and Winkler, ME (2002) Positive growth rate-dependent regulation of the pdxA, ksgA, and pdxB genes of Escherichia coli K-12.J. Bacteriol. 184:1359-69
Abstract	We found that transcription of the pdxA and pdxB genes, which mediate steps in the biosynthesis of the essential coenzyme pyridoxal 5"-phosphate, and the ksgA gene, which encodes an rRNA modification enzyme and is partly cotranscribed with pdxA, is subject to positive growth rate regulation in Escherichia coli K-12. The amounts of the pdxA-ksgA cotranscript and pdxB- and ksgA-specific transcripts and expression from pdxA- and pdxB-lacZ fusions increased as the growth rate increased. The half-lives of ksgA- and pdxB-specific transcripts were not affected by the growth rate, whereas the half-life of the pdxA-ksgA cotranscript was too short to be measured accurately. A method of normalization was applied to determine the amount of mRNA synthesized per gene and the rate of protein accumulation per gene. Normalization removed an apparent anomaly at fast growth rates and demonstrated that positive regulation of pdxB occurs at the level of transcription initiation over the whole range of growth rates tested. RNA polymerase limitation and autoregulation could not account for the positive growth rate regulation of pdxA, pdxB, and ksgA transcription. On the other hand, growth rate regulation of the amount of the pdxA-ksgA cotranscript was abolished by a fis mutation, suggesting a role for the Fis protein. In contrast, the fis mutation had no effect on pdxB- or ksgA-specific transcript amounts. The amounts of the pdxA-ksgA cotranscript and ksgA-specific transcript were repressed in the presence of high intracellular concentrations of guanosine tetraphosphate; however, this effect was independent of relA function for the pdxA-ksgA cotranscript. Amounts of the pdxB-specific transcript remained unchanged during amino acid starvation in wild-type and relA mutant strains.
Links	PubMed
Keywords	Bacterial Proteins; Carbohydrate Dehydrogenases; Carrier Proteins; Culture Media; Escherichia coli; Escherichia coli Proteins; Factor For Inversion Stimulation Protein; Gene Expression Regulation, Bacterial; Guanosine Tetraphosphate; Integration Host Factors; Methyltransferases; Mutation; Oxidoreductases; Pyridoxal Phosphate; Recombinant Fusion Proteins; Transcription, Genetic
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Phenotype of	Taxon Information	Genotype Information (if known)	Condition Information	OMP ID	OMP Term Name	ECO ID	ECO Term Name	Notes	Status
	Taxon: Escherichia coli Strain: K-12 Substrain: NU1187 NCBI Taxon ID: 83333	Genotype of Reference Strain: pdxA Genotype of Experimental Strain : pdxA:minimudI lacZ	Reference Condition:					Proximal surface mutation exhibit a 2.3 to 3.2-fold decrease in affinity to DsrA, a small regulatory RNA, compared to wildtype Hfq. Thus translation cannot continue because DsrA is required in order to enhance translation of rpoS mRNA which encodes a transcription factor, table 1.
	Taxon: Escherichia coli Strain: K-12 Substrain: NU1702 NCBI Taxon ID: 83333	Genotype of Reference Strain: pdxB Genotype of Experimental Strain : pdxB:minimudIacZ	Reference Condition:					Mutants with lacZ translation fusion showed expression of pdxB incease in proportion to the growth rate, Fig 2. expression leads to PLP biosynthesis.
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