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J. Bacteriol., 03 1995, 1452-1460, Vol 177, No. 6
M Osteras, BT Driscoll and TM Finan
The pckA gene of Rhizobium meliloti, encoding phosphoenolpyruvate
carboxykinase, was isolated from a genomic cosmid library by
complementation of the succinate growth phenotype of a Pck- mutant. The
gene region was mapped by subcloning and Tn5 insertion mutagenesis. The DNA
sequence for a 2-kb region containing the structural gene and its promoter
was determined. The pckA gene encodes as 536-amino-acid protein that shows
homology with other ATP-dependent Pck enzymes. The promoter was identified
following primer extension analysis and is similar to sigma 70-like
promoters. Expression analysis with a pckA::lacZ gene fusion indicated that
the pckA gene was strongly induced at the onset of stationary phase in
complex medium. When defined carbon sources were tested, the expression
level of the pckA gene was found to be high when cells were grown in
minimal media with succinate or arabinose as the sole carbon source but
almost absent when glucose, sucrose, or glycerol was the sole carbon
source. Glucose and sucrose were not found to strongly repress pckA
induction by succinate.
Copyright © 1995, American Society for Microbiology
Molecular and expression analysis of the Rhizobium meliloti phosphoenolpyruvate carboxykinase (pckA) gene
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
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