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Gene Review

hmp  -  fused nitric oxide dioxygenase/dihydropter...

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK2549, JW2536, fsrB, hmpA
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Disease relevance of hmp

  • We conclude that E. coli produces a soluble haemoglobin-like protein, the product of the hmp gene (for haemoprotein) [1].
  • The Mycobacterium tuberculosis hmp gene encodes a protein which is homologous to flavohemoglobin in Escherichia coli [2].

High impact information on hmp

  • In aerobic cultures, only 17 genes were significantly up-regulated, including genes known to be involved in NO tolerance, particularly hmp (encoding the NO-consuming flavohemoglobin Hmp) and norV (encoding flavorubredoxin) [3].
  • Viability of the hmp mutant in the presence of lethal concentrations of sodium nitroprusside was increased (to 30% survival after 2 h in 5 mM sodium nitroprusside) by overexpressing Vgb or the HD [4].
  • The model is supported by the inability of an fnr mutant to generate NO and by the restoration of NO accumulation to hmp mutants upon introducing a plasmid encoding Fnr* (D154A) known to confer activity in the presence of oxygen [5].
  • Cellular respiration of the hmp mutant was instantaneously inhibited in the presence of 13.5 microM NO but remained insensitive to NO inhibition when these cells overexpressed Hmp [4].
  • To determine the contribution of each domain of Hmp toward NO detoxification, we genetically engineered the Hmp protein and separately expressed the heme (HD) and the flavin (FD) domains in a defined hmp mutant [4].

Chemical compound and disease context of hmp


Biological context of hmp


Associations of hmp with chemical compounds

  • We now show that hmp expression is also upregulated by S-nitrosoglutathione (GSNO, widely used as an NO releaser) and sodium nitroprusside (SNP, which is a NO+ donor) [6].
  • As GSNO and SNP upregulate hmp similarly, the NO released in the former case on reaction with homocysteine cannot be involved in hmp regulation [6].
  • A monolysogen containing an hmp-lacZ operon fusion was constructed to determine how the hmp promoter is regulated in response to heme ligands (O2, NO) or the presence of anaerobically utilized electron acceptors (nitrate, nitrite) [7].
  • Other known superoxide-generating agents (plumbagin, menadione, and phenazine methosulfate) were not effective in inducing hmp expression [10].
  • These observations of hmp mRNA induction in response to O2 limitation and nitrosative stress suggest that the hmp gene of M. tuberculosis may have a role in protection of the organism from NO killing under microaerophilic conditions [2].

Other interactions of hmp

  • Anaerobic, but not aerobic, expression of phi (hmp-lacZ)1 was stimulated three- to four-fold by an fnr mutation; an apparent Fnr-binding site is present in the hmp promoter [7].
  • However, a mutation in rpoS did not prevent an increase in hmp expression by paraquat in exponentially growing cells [10].
  • Mutations in oxyR or rob, known regulators of several stress promoters in E. coli, had no effect on the induction of hmp by paraquat [10].
  • The hmp promoter is more sensitive to SNP and S-nitroso-N-penicillamine (SNAP) than is the soxS promoter, consistent with the role of Hmp in protection from reactive nitrogen species [9].
  • In vivo, sodA-lacZ fusion activity was increased 3-fold by introducing plasmid pPL341, containing the hmp gene, or by growth with paraquat [11].

Analytical, diagnostic and therapeutic context of hmp

  • Northern blotting analysis demonstrated that hmp transcription increased when a microaerophilic culture became oxygen limited as it entered stationary phase at 20 days [2].


  1. Isolation and nucleotide sequence of the hmp gene that encodes a haemoglobin-like protein in Escherichia coli K-12. Vasudevan, S.G., Armarego, W.L., Shaw, D.C., Lilley, P.E., Dixon, N.E., Poole, R.K. Mol. Gen. Genet. (1991) [Pubmed]
  2. Regulation of hmp gene transcription in Mycobacterium tuberculosis: effects of oxygen limitation and nitrosative and oxidative stress. Hu, Y., Butcher, P.D., Mangan, J.A., Rajandream, M.A., Coates, A.R. J. Bacteriol. (1999) [Pubmed]
  3. Transcriptional responses of Escherichia coli to S-nitrosoglutathione under defined chemostat conditions reveal major changes in methionine biosynthesis. Flatley, J., Barrett, J., Pullan, S.T., Hughes, M.N., Green, J., Poole, R.K. J. Biol. Chem. (2005) [Pubmed]
  4. Flavohemoglobin Hmp, but not its individual domains, confers protection from respiratory inhibition by nitric oxide in Escherichia coli. Hernández-Urzúa, E., Mills, C.E., White, G.P., Contreras-Zentella, M.L., Escamilla, E., Vasudevan, S.G., Membrillo-Hernández, J., Poole, R.K. J. Biol. Chem. (2003) [Pubmed]
  5. Nitric oxide formation by Escherichia coli. Dependence on nitrite reductase, the NO-sensing regulator Fnr, and flavohemoglobin Hmp. Corker, H., Poole, R.K. J. Biol. Chem. (2003) [Pubmed]
  6. A novel mechanism for upregulation of the Escherichia coli K-12 hmp (flavohaemoglobin) gene by the 'NO releaser', S-nitrosoglutathione: nitrosation of homocysteine and modulation of MetR binding to the glyA-hmp intergenic region. Membrillo-Hernández, J., Coopamah, M.D., Channa, A., Hughes, M.N., Poole, R.K. Mol. Microbiol. (1998) [Pubmed]
  7. Nitric oxide, nitrite, and Fnr regulation of hmp (flavohemoglobin) gene expression in Escherichia coli K-12. Poole, R.K., Anjum, M.F., Membrillo-Hernández, J., Kim, S.O., Hughes, M.N., Stewart, V. J. Bacteriol. (1996) [Pubmed]
  8. Reactions of the Escherichia coli flavohaemoglobin (Hmp) with NADH and near-micromolar oxygen: oxygen affinity of NADH oxidase activity. Poole, R.K., Ioannidis, N., Orii, Y. Microbiology (Reading, Engl.) (1996) [Pubmed]
  9. The flavohemoglobin of Escherichia coli confers resistance to a nitrosating agent, a "Nitric oxide Releaser," and paraquat and is essential for transcriptional responses to oxidative stress. Membrillo-Hernández, J., Coopamah, M.D., Anjum, M.F., Stevanin, T.M., Kelly, A., Hughes, M.N., Poole, R.K. J. Biol. Chem. (1999) [Pubmed]
  10. Paraquat regulation of hmp (flavohemoglobin) gene expression in Escherichia coli K-12 is SoxRS independent but modulated by sigma S. Membrillo-Hernández, J., Kim, S.O., Cook, G.M., Poole, R.K. J. Bacteriol. (1997) [Pubmed]
  11. The flavohaemoglobin (HMP) of Escherichia coli generates superoxide in vitro and causes oxidative stress in vivo. Membrillo-Hernández, J., Ioannidis, N., Poole, R.K. FEBS Lett. (1996) [Pubmed]
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