Disease relevance of nahR

• Surprisingly, amplified intergenic regions from naphthalene-degrading micro-organisms native to this study site were 100% identical to that of the pDTG1 plasmid (an archetypal naphthalene-catabolic plasmid from Pseudomonas putida NCIB 9816-4), but the nahR coding regions were not [1].
• Sequences similar to the consensus sequences of Escherichia coli promoters (at -35 and -10) were found in nah, sal, and nahR at the appropriate positions [2].
• Complementation with the closely related regulators NagR (from Ralstonia sp. strain U2) and NahR restored only induction by the archetype inducers, salicylate or salicylate and anthranilate, respectively, and did not restore the high basal level of expression of 2NTDO [3].
• A computer search for homologous proteins showed that within the first 124 amino-terminal residues, NahR has approximately 35% identity with the transcriptional activator proteins encoded by the nodD genes of Rhizobium species [4].
• Thus, our data indicated that NahR in P. putida Cg1 is virtually identical to its homologues in other pseudomonads and that nahR is required for resistance to naphthalene toxicity, hence the persistence of bacterial cells in soil with high concentrations of naphthalene [5].

High impact information on nahR

• Since expression of both of these operons is coordinately controlled by the product of the transcriptional activator gene nahR, the sequences were compared to locate potential sites involved in common regulation [2].
• In addition, the transcription start site of the nahR regulatory gene was located and its promoter sequence was determined [2].
• The bphR2 gene was not located near the bph gene cluster, and its product (BphR2) exhibited a high level of similarity to NahR (the naphthalene- and salicylate-catabolic regulator belonging to the LysR family) in plasmid NAH7 of Pseudomonas putida [6].
• The extracted DNA was used to successfully amplify nahR, the regulatory gene for naphthalene catabolism in Pseudomonas putida G7, by PCR.(ABSTRACT TRUNCATED AT 250 WORDS)[7]
• The DNA sequence of the nahR gene was determined, and a derived amino acid sequence of the NahR protein was obtained [4].

Chemical compound and disease context of nahR

• Analysis of expression of nahA from the nah promoter in either Escherichia coli or Pseudomonas putida showed that a 1.6-kb DNA fragment from the nahR (nah operon regulatory locus) region was required in trans for (i) induction by salicylate; (ii) high-level expression of nahA, and (iii) complementation of nahR- mutants [8].

Biological context of nahR

• In Pseudomonas putida strain G7, a LysR-type positive transcriptional activator protein encoded by nahR is necessary for activation of two operons involved in naphthalene catabolism [Schell, M. A. & Poser, E. F. (1989). J Bacteriol 171, 837-846] [1].
• Alignment of the deduced amino acid sequences from NahR homologues revealed that NahR-like proteins showed only minor variations in all investigated naphthalene-degrading isolates [1].
• Double transformants containing structural and regulatory cistron nahR in trans are used to demonstrate positive control of expression [9].
• After 21 days, loss of cell viability was pronounced in the presence of added naphthalene crystals for nahR mutants of both test bacteria, relative to the wild types [5].
• The naphthalene dioxygenase, including all the sequences for its expression and the regulatory region, has been localized on the 4.3-kb HindIII-ClaI fragment and on the 3.5-kb HindIII fragment of the plasmid pN3, by Southern analysis using as probes nahA and nahR genes, the homologous genes of the plasmid NAH7 from Pseudomonas putida G7 [10].

Associations of nahR with chemical compounds

• Targeted disruption of NCIB-nahR by homologous recombination resulted in a growth defect in the presence of naphthalene or salicylate as sole carbon and energy source [1].
• We found that all mutants responded to induction by both salicylate and benzoate, whereas the wild-type NahR responded only to salicylate [11].

Other interactions of nahR

• Thus, the structure and function of nahR-nahG regulatory genes appear to be highly conserved [1].

Analytical, diagnostic and therapeutic context of nahR

• The sediment-derived PCR products were sequenced and also found to be almost identical to known nahR genes [1].
• A gel mobility shift assay was used to identify a DNA-binding activity which was present only in extracts from either P. putida or Escherichia coli containing a functional nahR gene [12].

References