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Gene Review

nfxB  -  transcriptional regulator NfxB

Pseudomonas aeruginosa PAO1

 
 
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Disease relevance of nfxB

  • Three types of multiple-drug-resistant mutants which were phenotypically similar to previously described nalB, nfxB, and nfxC mutants were isolated from Pseudomonas aeruginosa PAO1 and two clinical isolates [1].
  • Expression of the phi (nfxB'-lacZ+) (Hyb) gene was repressed in the presence of the nfxB gene product provided by a second compatible plasmid in E. coli [2].
  • Certain genes from Lactococcus lactis and Pseudomonas aeruginosa, including the nfxB gene, generate a mutator phenotype in Escherichia coli [3].
 

High impact information on nfxB

  • Sequencing upstream of mexC revealed the presence of the nfxB gene transcribed divergently from the efflux genes [4].
  • Overexpression of the mexC-mexD-oprJ efflux operon in nfxB-type multidrug-resistant strains of Pseudomonas aeruginosa [4].
  • Overproduction of OprJ and the attendant multiple-antibiotic resistance of strain K385 was shown to result from a point mutation in nfxB, resulting in a H87-->R change in the predicted NfxB polypeptide [4].
  • Hypersusceptibility of the Pseudomonas aeruginosa nfxB mutant to beta-lactams due to reduced expression of the ampC beta-lactamase [5].
  • Cross-resistance between triclosan and antibiotics in Pseudomonas aeruginosa is mediated by multidrug efflux pumps: exposure of a susceptible mutant strain to triclosan selects nfxB mutants overexpressing MexCD-OprJ [6].
 

Chemical compound and disease context of nfxB

 

Biological context of nfxB

  • The susceptibilities of both type A and type B mutants were restored to the level of PAO1 by transformation with plasmid pNF111, which contained the wild-type nfxB gene, demonstrating that they are NfxB mutants [8].
  • These results suggest that there are at least two nfxB mutations that show different phenotypes and that production of OprJ is associated with changes in susceptibilities of NfxB mutants [8].
  • Two norfloxacin resistance genes, nfxA and nfxB, were mapped hex-9001 and leu-9005 and between pro-9031 and ilv-9023, respectively, on the P. aeruginosa PAO chromosome [9].
  • To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in P. aeruginosa, a site-specific deletion method was employed to remove the mexA-mexB-oprM region from the chromosome of wild-type and nfxB strains of P. aeruginosa [10].
  • Overproduction of the MDR determinants MexABOprM (nalB mutant) and MexCDOprJ (nfxB mutant) decreased the survival in water, the production of phenazines and proteases, and the virulence (using a Caenorhabditis elegans model system) of the P. aeruginosa mutants [11].
 

Anatomical context of nfxB

 

Associations of nfxB with chemical compounds

  • Type 2 (nfxB-type) mutants showed cross-resistance to quinolones and new cephems, i.e., cefpirome and cefozopran, concomitant with overproduction of an outer membrane protein with an apparent molecular mass of 54 kDa (OprJ) [1].
  • Whereas thiolactomycin was not a substrate of the MexCD-OprJ pump expressed in a delta(mexAB-oprM) nfxB mutant, cerulenin was efficiently effluxed by the MexCD-OprJ system [13].
  • The nfxB mutant showed a 16-fold increase in resistance to norfloxacin and a slight increase in resistance to nalidixic acid [9].
  • The resulting patterns of MICs of NFLX, beta-lactams, aminoglycosides, and chloramphenicol and the observed increased accumulation of NFLX were consistent with the occurrence of the nfxB type mutation in these clinical isolates [14].
  • When the outer membrane barrier was dismantled by the EDTA treatment, wild-type, nfxC, nfxB, and nalB strains showed significantly different levels of dye accumulation [15].
 

Other interactions of nfxB

  • In fact, transformation of the oprJ mutant with an OprM-expression plasmid decreased the former's susceptibility to the levels exhibited by the nfxB mutant without affecting the substrate specificity of MexCD-OprJ [16].
  • P. aeruginosa strains (norfloxacin MICs, 3.13 to 200 micrograms/ml) were transformed by either pPAW207 or pNF111 plasmid DNA, which included either the gyrA or nfxB gene, respectively [17].
  • Four strains had mexR and two strains nfxB mutations [18].
 

Analytical, diagnostic and therapeutic context of nfxB

  • In the P. aeruginosa wild-type strain (PAO2142), NfxB was undetectable by immunoblotting; however, it was detected in the nfxB missense mutant (PK1013E) [2].

References

  1. Outer membrane proteins responsible for multiple drug resistance in Pseudomonas aeruginosa. Masuda, N., Sakagawa, E., Ohya, S. Antimicrob. Agents Chemother. (1995) [Pubmed]
  2. Purification and characterization of the Pseudomonas aeruginosa NfxB protein, the negative regulator of the nfxB gene. Shiba, T., Ishiguro, K., Takemoto, N., Koibuchi, H., Sugimoto, K. J. Bacteriol. (1995) [Pubmed]
  3. Mutator effects in Escherichia coli caused by the expression of specific foreign genes. Gabrovsky, V., Yamamoto, M.L., Miller, J.H. J. Bacteriol. (2005) [Pubmed]
  4. Overexpression of the mexC-mexD-oprJ efflux operon in nfxB-type multidrug-resistant strains of Pseudomonas aeruginosa. Poole, K., Gotoh, N., Tsujimoto, H., Zhao, Q., Wada, A., Yamasaki, T., Neshat, S., Yamagishi, J., Li, X.Z., Nishino, T. Mol. Microbiol. (1996) [Pubmed]
  5. Hypersusceptibility of the Pseudomonas aeruginosa nfxB mutant to beta-lactams due to reduced expression of the ampC beta-lactamase. Masuda, N., Sakagawa, E., Ohya, S., Gotoh, N., Nishino, T. Antimicrob. Agents Chemother. (2001) [Pubmed]
  6. Cross-resistance between triclosan and antibiotics in Pseudomonas aeruginosa is mediated by multidrug efflux pumps: exposure of a susceptible mutant strain to triclosan selects nfxB mutants overexpressing MexCD-OprJ. Chuanchuen, R., Beinlich, K., Hoang, T.T., Becher, A., Karkhoff-Schweizer, R.R., Schweizer, H.P. Antimicrob. Agents Chemother. (2001) [Pubmed]
  7. Purification of a 54-kilodalton protein (OprJ) produced in NfxB mutants of Pseudomonas aeruginosa and production of a monoclonal antibody specific to OprJ. Hosaka, M., Gotoh, N., Nishino, T. Antimicrob. Agents Chemother. (1995) [Pubmed]
  8. Quantitative correlation between susceptibility and OprJ production in NfxB mutants of Pseudomonas aeruginosa. Masuda, N., Gotoh, N., Ohya, S., Nishino, T. Antimicrob. Agents Chemother. (1996) [Pubmed]
  9. Mutations producing resistance to norfloxacin in Pseudomonas aeruginosa. Hirai, K., Suzue, S., Irikura, T., Iyobe, S., Mitsuhashi, S. Antimicrob. Agents Chemother. (1987) [Pubmed]
  10. Characterization of the MexC-MexD-OprJ multidrug efflux system in DeltamexA-mexB-oprM mutants of Pseudomonas aeruginosa. Gotoh, N., Tsujimoto, H., Tsuda, M., Okamoto, K., Nomura, A., Wada, T., Nakahashi, M., Nishino, T. Antimicrob. Agents Chemother. (1998) [Pubmed]
  11. Fitness of in vitro selected Pseudomonas aeruginosa nalB and nfxB multidrug resistant mutants. Sánchez, P., Linares, J.F., Ruiz-Díez, B., Campanario, E., Navas, A., Baquero, F., Martínez, J.L. J. Antimicrob. Chemother. (2002) [Pubmed]
  12. Cloning and nucleotide sequence of the Pseudomonas aeruginosa nfxB gene, conferring resistance to new quinolones. Okazaki, T., Hirai, K. FEMS Microbiol. Lett. (1992) [Pubmed]
  13. Intrinsic resistance to inhibitors of fatty acid biosynthesis in Pseudomonas aeruginosa is due to efflux: application of a novel technique for generation of unmarked chromosomal mutations for the study of efflux systems. Schweizer, H.P. Antimicrob. Agents Chemother. (1998) [Pubmed]
  14. Occurrence of the nfxB type mutation in clinical isolates of Pseudomonas aeruginosa. Jakics, E.B., Iyobe, S., Hirai, K., Fukuda, H., Hashimoto, H. Antimicrob. Agents Chemother. (1992) [Pubmed]
  15. Interplay between the efflux pump and the outer membrane permeability barrier in fluorescent dye accumulation in Pseudomonas aeruginosa. Germ, M., Yoshihara, E., Yoneyama, H., Nakae, T. Biochem. Biophys. Res. Commun. (1999) [Pubmed]
  16. Functional replacement of OprJ by OprM in the MexCD-OprJ multidrug efflux system of Pseudomonas aeruginosa. Gotoh, N., Tsujimoto, H., Nomura, A., Okamoto, K., Tsuda, M., Nishino, T. FEMS Microbiol. Lett. (1998) [Pubmed]
  17. Mechanisms of high-level resistance to quinolones in urinary tract isolates of Pseudomonas aeruginosa. Yoshida, T., Muratani, T., Iyobe, S., Mitsuhashi, S. Antimicrob. Agents Chemother. (1994) [Pubmed]
  18. Mechanisms of quinolone resistance in clinical strains of Pseudomonas aeruginosa. Jalal, S., Wretlind, B. Microb. Drug Resist. (1998) [Pubmed]
 
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