Affiliation:
1. Department of Microbiology and Molecular Genetics, University of Texas Houston Medical School, Houston, Texas 77030-1501
Abstract
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
21 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献