Evidence of Multiple Regulatory Functions for the PtsN (IIA Ntr ) Protein of Pseudomonas putida

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Abstract
The ptsN gene of Pseudomonas putida encodes IIA Ntr , a protein of the phosphoenol pyruvate:sugar phosphotransferase (PTS) system which is required for the C source inhibition of the ς 54 -dependent promoter Pu of the TOL (toluate degradation) plasmid pWW0. Using two-dimensional gel electrophoresis, we have examined the effect of ptsN disruption on the general expression pattern of P. putida . To this end, cells were grown in the presence or absence of glucose, and a 1,117-spot subset of the P. putida proteome was used as a reference for comparisons. Among all gene products whose expression was lowered by this carbon source (247 spots [about 22%]), only 6 behaved as Pu (i.e., were depressed in the ptsN background). This evidenced only a minor role for IIA Ntr in the extensive inhibition of gene expression in P. putida caused by glucose. However, the same experiments revealed a large incidence of glucose-independent effects brought about by the ptsN mutation. As many as 108 spots (ca. 9% of the cell products analyzed) were influenced, positively or negatively, by the loss of IIA Ntr . By matching this pattern with that of an rpoN ::ΩKm strain of P. putida , which lacks the ς 54 protein, we judge that most proteins whose expression was affected by ptsN were unrelated to the alternative sigma factor. These data suggest a role of IIA Ntr as a general regulator, independent of the presence of repressive carbon sources and not limited to ς 54 -dependent genes.