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J. Bacteriol., 07 1997, 4501-4512, Vol 179, No. 14
A Treuner-Lange, A Kuhn and P Durre
The complete sequence of the kdp gene region of Clostridium acetobutylicum
has been determined. This part of the chromosome comprises two small open
reading frames (orfZ and orfY), putatively encoding hydrophobic peptides,
and the genes kdpA, kdpB, kdpC, and kdpX, followed by an operon encoding a
pair of sensor-effector regulatory proteins (KdpD and KdpE). Except for
orfZ, orfY, and kdpX, all genes showed significant homology to the kdp
genes of Escherichia coli, encoding a high-affinity potassium transport
ATPase and its regulators. The complete genome sequence of Synechocystis
sp. strain PCC 6803 and a recently published part of the Mycobacterium
tuberculosis genome indicate the existence of a kdp system in these
organisms as well, but all three systems comprise neither a second orf
upstream of kdpA nor an additional kdpX gene. Expression of the clostridial
kdp genes, including the unique kdpX gene, was found to be inducible by low
potassium concentrations. A transcription start point could be mapped
upstream of orfZ. A promoter upstream of kdpD was active only under
noninducing conditions. Lowering the potassium content of the medium led to
formation of a common transcript (orfZYkdpABCXDE), with a putative internal
RNase E recognition site, which could be responsible for the instability of
the common transcript. Except for the two small peptides, all gene products
could be detected in in vitro transcription-translation experiments.
Copyright © 1997, American Society for Microbiology
The kdp system of Clostridium acetobutylicum: cloning, sequencing, and transcriptional regulation in response to potassium concentration
Angewandte Mikrobiologie und Mykologie, Universitat Ulm, Germany.
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