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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
Gene Review

orfX  -  hypothetical protein

Escherichia coli

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Disease relevance of orfX

  • When orfX was expressed from a phage T7 promoter in E. coli, a protein with an apparent molecular mass of approximately 18 kDa was produced [1].
  • The first, orfX, is predicted to encode a 105-amino-acid polypeptide that is similar to MopB, a protein which is required for both motility and virulence in Erwinia carotovora [2].
  • The N-terminus of the ORFs is similar to a putative glycoprotease in Pasteurella haemolytica and its homologue in Escherichia coli, the orfX gene [3].
  • The smaller open reading frame, orfX, also observed in Streptomyces coelicolor and Streptomyces avermitilis, may be translationally coupled to pnp and the gene downstream from pnp, a putative protease [4].

High impact information on orfX

  • Disruption of orfX had no effect on growth but caused a sporulation defect, characterized by low sporulation frequencies and heat-sensitive spores, which could be cured by supplementation with dipicolinate, similar to the phenotype of mutants defective in spoVF, the putative structural gene for dipicolinate synthase [5].
  • The orfX gene product was shown not to be directly linked to the lysine biosynthetic pathway, nor is it the enzyme incorporating DAP into the peptidoglycan precursor [6].
  • Through the use of transcriptional fusions, none of the putative tol (or tol-associated) genes were shown to be regulated by PhoPQ, bile, or the RcsC-RcsB two-component system; however, all of the genes (orfX, orf1, tolQRA) are predicted to be cotranscribed [7].
  • Via the N-terminal amino-acid sequence, the MtdB encoding gene was identified to be orfX located in a cluster of genes whose translated products show high sequence identities to enzymes previously found only in methanogenic and sulfate reducing archaea [8].
  • Reverse transcriptase-PCR analysis indicated that flbF through to orfX are transcribed as a single mRNA, and primer extension analysis revealed that transcription of the flgK operon is initiated by a sigma 70-like promoter upstream of flbF [9].

Chemical compound and disease context of orfX

  • The deduced products of four of these ORFs were homologous to components of the glucitol phosphotransferase system (PTS) and glucitol 6-phosphate dehydrogenase from E. coli, while the remaining ORF (orfX) encoded an enzyme which had similarities to members of a family of transaldolases [10].

Biological context of orfX

  • Nucleotide sequence analysis of the region 5' to vfr identified a 423-bp open reading frame (ORF), which was designated orfX [1].
  • The transcriptional start point determined by primer extension analysis suggested that -10 and -35 regions are present upstream of orfX and are very similar to the consensus sequence for the sigma k-dependent promoter [11].
  • The latter consists of two monocistronic operons gtaB and orfX, transcribed from a 245 bp regulatory region, each encoding an acidic protein with a molecular mass of 33.0 and 42.6 kDa, respectively. gtaB is transcribed from a distal PA promoter, and a proximal PB promoter which is negatively controlled by the Sin protein [12].


  1. A divergently transcribed open reading frame is located upstream of the Pseudomonas aeruginosa vfr gene, a homolog of Escherichia coli crp. Runyen-Janecky, L.J., Sample, A.K., Maleniak, T.C., West, S.E. J. Bacteriol. (1997) [Pubmed]
  2. Temporal and spatial regulation of fliP, an early flagellar gene of Caulobacter crescentus that is required for motility and normal cell division. Gober, J.W., Boyd, C.H., Jarvis, M., Mangan, E.K., Rizzo, M.F., Wingrove, J.A. J. Bacteriol. (1995) [Pubmed]
  3. Identification of a eukaryotic-like protein kinase gene in Archaebacteria. Smith, R.F., King, K.Y. Protein Sci. (1995) [Pubmed]
  4. Organization and expression of the polynucleotide phosphorylase gene (pnp) of Streptomyces: Processing of pnp transcripts in Streptomyces antibioticus. Bralley, P., Jones, G.H. J. Bacteriol. (2004) [Pubmed]
  5. Organization and nucleotide sequence of the Bacillus subtilis diaminopimelate operon, a cluster of genes encoding the first three enzymes of diaminopimelate synthesis and dipicolinate synthase. Chen, N.Y., Jiang, S.Q., Klein, D.A., Paulus, H. J. Biol. Chem. (1993) [Pubmed]
  6. Nucleotide sequence and organization of the upstream region of the Corynebacterium glutamicum lysA gene. Marcel, T., Archer, J.A., Mengin-Lecreulx, D., Sinskey, A.J. Mol. Microbiol. (1990) [Pubmed]
  7. Salmonella enterica serovar typhimurium resistance to bile: identification and characterization of the tolQRA cluster. Prouty, A.M., Van Velkinburgh, J.C., Gunn, J.S. J. Bacteriol. (2002) [Pubmed]
  8. Characterization of a second methylene tetrahydromethanopterin dehydrogenase from Methylobacterium extorquens AM1. Hagemeier, C.H., Chistoserdova, L., Lidstrom, M.E., Thauer, R.K., Vorholt, J.A. Eur. J. Biochem. (2000) [Pubmed]
  9. The flgK motility operon of Borrelia burgdorferi is initiated by a sigma 70-like promoter. Ge, Y., Old, I.G., Girons, I.S., Charon, N.W. Microbiology (Reading, Engl.) (1997) [Pubmed]
  10. A gene system for glucitol transport and metabolism in Clostridium beijerinckii NCIMB 8052. Tangney, M., Brehm, J.K., Minton, N.P., Mitchell, W.J. Appl. Environ. Microbiol. (1998) [Pubmed]
  11. A Bacillus subtilis spore coat polypeptide gene, cotS. Abe, A., Koide, H., Kohno, T., Watabe, K. Microbiology (Reading, Engl.) (1995) [Pubmed]
  12. Sequencing and analysis of the divergon comprising gtaB, the structural gene of UDP-glucose pyrophosphorylase of Bacillus subtilis 168. Soldo, B., Lazarevic, V., Margot, P., Karamata, D. J. Gen. Microbiol. (1993) [Pubmed]
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