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Journal of Bacteriology, September 2001, p. 5128-5133, Vol. 183, No. 17
Centro Nacional de Biotecnología del
CSIC, Madrid 28049, Spain
Received 9 April 2001/Accepted 6 June 2001
An investigation was made into the role of the ptsO
gene in carbon source inhibition of the Pu promoter
belonging to the Pseudomonas putida upper TOL (toluene
degradation) operon. ptsO is coexpressed with
ptsN, the loss of which is known to render
Pu unresponsive to glucose. Both ptsN and
ptsO, coding for the phosphoenolpyruvate:sugar phosphotransferase system (PTS) family proteins
IIANtr and NPr, respectively, have been mapped adjacent to
the rpoN gene of P. putida. The roles of
these two genes in the responses of Pu to glucose were
monitored by lacZ reporter technology with a P.
putida strain engineered with all regulatory elements in monocopy gene dosage. In cells lacking ptsO,
Pu activity seemed to be inhibited even in the absence
of glucose. A functional relationship with ptsN
was revealed by the phenotype of a double ptsN ptsO mutant that was equivalent to the phenotype of a mutant with a single
ptsN disruption. Moreover, phosphorylation of the
product of ptsO seemed to be required for C inhibition
of Pu, since an H15A change in the NPr sequence that
prevents phosphorylation of this conserved amino acid residue did not
restore the wild-type phenotype. A genomic search for proteins able to
phosphorylate ptsO revealed the presence of two open
reading frames, designated ptsP and mtp,
with the potential to encode PTS type I enzymes in P.
putida. However, neither an insertion in ptsP
nor an insertion in mtp resulted in a detectable change
in inhibition of Pu by glucose. These results indicate
that some PTS proteins have regulatory functions in P.
putida that are independent of their recognized role in sugar
transport in other bacteria.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.17.5128-5133.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of ptsO in Carbon-Mediated
Inhibition of the Pu Promoter Belonging to the pWW0
Pseudomonas putida Plasmid
*
Corresponding author. Mailing address: Centro Nacional
de Biotecnología del CSIC, Campus de Cantoblanco, 28049 Madrid,
Spain. Phone: 34 91 585 4536. Fax: 34 91 585 4506. E-mail:
vdlorenzo{at}cnb.uam.es.
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