VHb (hemoglobin) explained

Vitreoscilla haemoglobin (VHb) is a type of haemoglobin found in the Gram-negative aerobic bacterium, Vitreoscilla. It is the first haemoglobin discovered from bacteria, but unlike classic haemoglobin it is composed only of a single globin molecule.[1] Like typical haemoglobin, its primary role is binding oxygen, but it also performs other functions including delivery of oxygen to oxygenases, detoxification of nitric oxide, sensing and relaying oxygen concentrations, peroxidase-like activity by eliminating autoxidation-derived H2O2 that prevents haeme degradation and iron release.

Discovery

In 1986, a bacterial (Vitreoscilla) heme protein that had been studied by Webster and his colleagues, was sequenced and this amino acid sequence exhibited the globin folds of a haemoglobin.[2] [3] It consists of a single domain which normally occurs as a dimer. The solution of its crystal structure confirmed that its 3-dimensional structure is remarkably similar to the classic globin fold.[4] When the gene (vgb) for this haemoglobin was cloned into E. coli[5] it was found that it increased the growth of these cells under low oxygen conditions compared to control bacteria.[6] The concentration of VHb drastically increased in Vitreoscilla, a strict aerobe, grown under hypoxic conditions,[7] and it was proposed that it acted as an "oxygen storage trap" to feed oxygen to the terminal oxidase (cytochrome bo) under these conditions.[8] Further evidence for this is that VHb is concentrated in vivo near the membrane of Vitreoscilla cells.[9] It was also shown that VHb binds to subunit I of the cytochrome bo terminal oxidase,[10] the heme-containing subunit that is also responsible for the unique sodium pumping function of this unique terminal oxidase.[11]

Function

VHb is the best understood of all the bacterial haemoglobins, and is attributed to play a number of functions. Its main role is likely the binding of oxygen at low concentrations and its direct delivery to the terminal respiratory oxidase(s) such as cytochrome o. It is also involved in the delivery of oxygen to oxygenases,[12] detoxification of nitric oxide by converting it to nitrate,[13] and sensing oxygen concentrations and passing this signal to transcription factors.[14] [15] It has a peroxidase-like activity and effectively eliminates autoxidation-derived H2O2, which is a cause of haeme degradation and iron release.[16]

Genetic regulation

The VHb gene, vgb, exists as a single copy in Vitreoscilla and exhibits complete agreement with the primary sequence of VHb.[17] The downstream region adjacent to vgb carries a gene in the opposite direction having close similarity with the uvrA gene of E. coli, indicating that vgb is not part of a multigene operon.[18] Biosynthesis of VHb is regulated at the transcriptional level and is induced under hypoxia in its native host.[19] vgb is expressed strongly in E. coli through its native promoter and a similar increase in its transcript level occurs under hypoxia; this suggests a close similarity in the transcriptional machinery of Vitreoscilla and E. coli.[20] The promoter region of vgb is crowded with overlapping binding sites for several redox-sensitive transcriptional regulators, involving the fumarate and nitrate reduction (Fnr) system as primary regulator. The catabolite repression (Crp) system is an additional control[21] along with the aerobic respiration control (Arc) system as a third oxygen-dependent controller.[22] Another binding site for the oxidative stress response regulator (OxyR) is also present within the vgb promoter; all these transcriptional regulators appear to work in coordination with each other to control the biosynthesis of VHb in a redox dependent manner.

Genetic engineering and applications

Since it was shown that VHb stimulated the growth of E. coli under hypoxic conditions, vgb was cloned into a variety of organisms, including various bacteria, yeast, fungi, and even higher plants and animals to test its effects on growth and production of products of potential commercial importance, the degradation of toxic compounds, the enhancement of nitrification in wastewater treatment, and other environmental applications.[23]

Examples of increased productivity include increased yield of a variety of biochemicals including antibiotics, an insecticide, a surfactant, and potential plastic feedstocks. They also include enzymes[24] (including one which might have anti-leukemic properties), and fuels (including ethanol,[25] butanediol,[26] [27] and biodiesel). The toxic compounds studied have been aromatics including 2-chlorobenzoic acid and 2,4-dinitrotolene.[28] [29] In these cases, increases in degradation are thought to be due both to the effects of VHb enhancing respiration to provide cells with additional ATP for growth and production of degrading enzymes, and delivery of oxygen directly to the oxygenases required for early steps in the degradative pathways.

Other environmental investigations include those related to heavy metal remediation and provision of soil phosphate to plants. Expression of vgb in Nitrosomonas europaea, a bacterium involved of conversion of ammonia to nitrite in wastewater, enhanced, to some degree, its ability in this conversion.[30] Furthermore, it was shown that the mechanism of haeme protein expression to enhance oxygen supply to the monooxygenase in nitrification under hypoxic conditions is similar to VHb function seen in other applications.[31]

Amino acid residues in several sections of VHb in proximity to the haeme were altered using genetic engineering to change VHb’s affinity for oxygen and to examine the effects on the biotechnological properties of some of the systems studied. Many of the mutations did not have large effects on the ligand binding properties of VHb, or provided at best a modest increase in cell growth compared with cells harboring wild type VHb.[32] Two of the mutant VHb’s, however, provided substantial increases in growth and aromatic compound degradation compared to wild type VHb in Pseudomonas and Burkholderia bacteria transformed to contain vgb.[33]

Notes and References

  1. Stark BC, Dikshit KL, Pagilla KR . The Biochemistry of Vitreoscilla hemoglobin . Computational and Structural Biotechnology Journal . 3 . 4 . e201210002 . 2012 . 10.5936/csbj.201210002 . 24688662 . 3962134 .
  2. Webster . Dale A. . Dikshit . Kanak L. . Pagilla . Krishna R. . Stark . Benjamin C. . August 2021 . The Discovery of Vitreoscilla Hemoglobin and Early Studies on Its Biochemical Functions, the Control of Its Expression, and Its Use in Practical Applications . Microorganisms . en . 9 . 8 . 1637 . 10.3390/microorganisms9081637 . free . 2076-2607 . 8398370 . 34442716.
  3. Wakabayashi . S. . Matsubara . H. . Webster . D. A. . July 1986 . Primary sequence of a dimeric bacterial haemoglobin from Vitreoscilla . Nature . en . 322 . 6078 . 481–483 . 10.1038/322481a0 . 3736670 . 1986Natur.322..481W . 1476-4687.
  4. Tarricone . Cataldo . Galizzi . Alessandro . Coda . Alessandro . Ascenzi . Paolo . Bolognesi . Martino . April 1997 . Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp . Structure . 5 . 4 . 497–507 . 10.1016/s0969-2126(97)00206-2 . 9115439 . 0969-2126. free .
  5. Dikshit . Kanak L. . Webster . Dale A. . 1988-10-30 . Cloning, characterization and expression of the bacterial globin gene from Vitreoscilla in Escherichia coli . Gene . 70 . 2 . 377–386 . 10.1016/0378-1119(88)90209-0 . 2850971 . 0378-1119.
  6. Webster . Dale A. . Dikshit . Kanak L. . Pagilla . Krishna R. . Stark . Benjamin C. . October 2021 . The Discovery of Vitreoscilla Hemoglobin and Early Studies on Its Biochemical Functions, the Control of Its Expression, and Its Use in Practical Applications . Microorganisms . en . 9 . 8 . 1637 . 10.3390/microorganisms9081637 . free . 2076-2607 . 8398370 . 34442716.
  7. Boerman . Scott J. . Webster . Dale A. . 1982 . Control of Heme Content in Vitreoscilla by Oxygen . The Journal of General and Applied Microbiology . 28 . 1 . 35–43 . 10.2323/jgam.28.35.
  8. Webster . Dale. A. . 1988 . Structure and function of bacterial hemoglobin and related proteins . Advances in Inorganic Biochemistry . 7 . 245–265 . 3275422.
  9. Ramandeep . Hwang . Kwang Woo . Raje . Manoj . Kim . Kyung-Jin . Stark . Benjamin C. . Dikshit . Kanak L. . Webster . Dale A. . January 2001 . Vitreoscilla Hemoglobin . Journal of Biological Chemistry . 276 . 27 . 24781–24789 . 11331274 . 10.1074/jbc.m009808200 . free . 0021-9258.
  10. Park . Kyung-Won . Kim . Kyung-Jin . Howard . Andrew J. . Stark . Benjamin C. . Webster . Dale A. . September 2002 . Vitreoscilla Hemoglobin Binds to Subunit I of Cytochrome bo Ubiquinol Oxidases . Journal of Biological Chemistry . 277 . 36 . 33334–33337 . 10.1074/jbc.m203820200 . free . 12080058 . 0021-9258.
  11. Chung . Yeon T. . Stark . Benjamin C. . Webster . Dale A. . 2006-10-06 . Role of Asp544 in subunit I for Na+ pumping by Vitreoscilla cytochrome bo . Biochemical and Biophysical Research Communications . 348 . 4 . 1209–1214 . 16919598 . 10.1016/j.bbrc.2006.07.184 . 0006-291X.
  12. Fish . Pamela A. . Webster . Dale A. . Stark . Benjamin C. . 2000-03-20 . Vitreoscilla hemoglobin enhances the first step in 2,4-dinitrotoluene degradation in vitro and at low aeration in vivo . Journal of Molecular Catalysis B: Enzymatic . 9 . 1 . 75–82 . 10.1016/S1381-1177(99)00086-7 . 1381-1177.
  13. Kaur . Ramandeep . Pathania . Ranjana . Sharma . Vishwamitra . Mande . Shekhar C. . Dikshit . Kanak L. . January 2002 . Chimeric Vitreoscilla Hemoglobin (VHb) Carrying a Flavoreductase Domain Relieves Nitrosative Stress in Escherichia coli : New Insight into the Functional Role of VHb . Applied and Environmental Microbiology . en . 68 . 1 . 152–160 . 2002ApEnM..68..152K . 10.1128/AEM.68.1.152-160.2002 . 0099-2240 . 126558 . 11772621.
  14. Anand . Arvind . Duk . Brian T. . Singh . Sandeep . Akbas . Meltem Y. . Webster . Dale A. . Stark . Benjamin C. . Dikshit . Kanak L. . 2010-02-24 . Redox-mediated interactions of VHb (Vitreoscilla haemoglobin) with OxyR: novel regulation of VHb biosynthesis under oxidative stress . Biochemical Journal . 426 . 3 . 271–280 . 10.1042/bj20091417 . 0264-6021 . 20025616.
  15. Stark BC, Dikshit KL, Pagilla KR . 2011 . Recent advances in understanding the structure, function, and biotechnological usefulness of the hemoglobin from the bacterium Vitreoscilla . Biotechnol Lett . 33 . 9 . 1705–1714 . 10.1007/s10529-011-0621-9 . 21603987.
  16. Isarankura-Na-Ayudhya C, Tansila N, Worachartcheewan A, Bülow L, Prachayasittikul V . Biochemical and cellular investigation of Vitreoscilla hemoglobin (VHb) variants possessing efficient peroxidase activity . J Microbiol Biotechnol . 20 . 3 . 532–541 . 2010 . 20372024.
  17. Webster . Dale A. . Dikshit . Kanak L. . Pagilla . Krishna R. . Stark . Benjamin C. . 2021 . The Discovery of Vitreoscilla Hemoglobin and Early Studies on Its Biochemical Functions, the Control of Its Expression, and Its Use in Practical Applications . Microorganisms . en . 9 . 8 . 1637 . 10.3390/microorganisms9081637 . free . 2076-2607 . 8398370 . 34442716.
  18. Liu . S. C. . Liu . Y. -X. . Webster . D. A. . Stark . B. C. . November 1994 . Sequence of the region downstream of the Vitreoscilla hemoglobin gene: vgb is not part of a multigene operon . Applied Microbiology and Biotechnology . en . 42 . 2 . 304–308 . 7765771 . 10.1007/BF00902733 . 1432-0614.
  19. Dikshit . Kanak L. . Spaulding . Douglas . Braun . Annette . Webster . Dale A. . 1989 . Oxygen Inhibition of Globin Gene Transcription and Bacterial Haemoglobin Synthesis in Vitreoscilla . Microbiology . 135 . 10 . 2601–2609 . 10.1099/00221287-135-10-2601 . free . 2483729 . 1465-2080.
  20. Dikshit . Kanak L. . Dikshit . Rajendra P. . Webster . Dale A. . 1990-07-25 . Study of Vitreoscilla globin(vgb) gene expression and promoter activity in E. Coli through transcriptional fusion . Nucleic Acids Research . 18 . 14 . 4149–4155 . 10.1093/nar/18.14.4149 . free . 0305-1048 . 331172 . 2198533.
  21. Joshi . M. . Dikshit . K. L. . 1994-07-15 . Oxygen-Dependent Regulation of Vitreoscilla Globin Gene: Evidence for Positive Regulation by FNR . Biochemical and Biophysical Research Communications . 202 . 1 . 535–542 . 10.1006/bbrc.1994.1961 . 8037759 . 0006-291X.
  22. Yang . Jianguo . Webster . Dale A. . Stark . Benjamin C. . 2005-10-03 . ArcA works with Fnr as a positive regulator of Vitreoscilla (bacterial) hemoglobin gene expression in Escherichia coli . Microbiological Research . 160 . 4 . 405–415 . 10.1016/j.micres.2005.03.004 . 16255146 . 0944-5013. free .
  23. Stark . Benjamin C. . Pagilla . Krishna R. . Dikshit . Kanak L. . 2015-02-01 . Recent applications of Vitreoscilla hemoglobin technology in bioproduct synthesis and bioremediation . Applied Microbiology and Biotechnology . en . 99 . 4 . 1627–1636 . 10.1007/s00253-014-6350-y . 25575886 . 1432-0614.
  24. Khosravi . Mahvash . Webster . Dale A. . Stark . Benjamin C. . November 1990 . Presence of the bacterial hemoglobin gene improves α-amylase production of a recombinant Escherichia coli strain . Plasmid . 24 . 3 . 190–194 . 10.1016/0147-619X(90)90002-T . 2136531 . 0147-619X.
  25. Sanny . Tony . Arnaldos . Marina . Kunkel . Stephanie A. . Pagilla . Krishna R. . Stark . Benjamin C. . November 2010 . Engineering of ethanolic E. coli with the Vitreoscilla hemoglobin gene enhances ethanol production from both glucose and xylose . Applied Microbiology and Biotechnology . en . 88 . 5 . 1103–1112 . 10.1007/s00253-010-2817-7 . 20717665 . 1432-0614.
  26. Wei . Mei-Ling . Webster . Dale A. . Stark . Benjamin C. . 1998-09-05 . Metabolic engineering of Serratia marcescens with the bacterial hemoglobin gene: Alterations in fermentation pathways . Biotechnology and Bioengineering . en . 59 . 5 . 640–646 . 10.1002/(SICI)1097-0290(19980905)59:5<640::AID-BIT15>3.0.CO;2-D. 10099382 .
  27. Geckil . Hikmet . Barak . Ze'ev . Chipman . David M. . Erenler . Sebnem O. . Webster . Dale A. . Stark . Benjamin C. . October 2004 . Enhanced production of acetoin and butanediol in recombinant Enterobacter aerogenes carrying Vitreoscilla hemoglobin gene . Bioprocess and Biosystems Engineering . en . 26 . 5 . 325–330 . 10.1007/s00449-004-0373-1 . 15309606 . 1615-7605.
  28. Urgun-Demirtas . Meltem . Pagilla . Krishna R. . Stark . Benjamin C. . Webster . Dale . October 2003 . Biodegradation of 2-Chlorobenzoate by Recombinant Burkholderia Cepacia Expressing Vitreoscilla Hemoglobin Under Variable Levels of Oxygen Availability . Biodegradation . en . 14 . 5 . 357–365 . 10.1023/A:1025672528291 . 14571952 . 1572-9729.
  29. So . Juho . Webster . Dale A. . Stark . Benjamin C. . Pagilla . Krishna R. . 2004-06-01 . Enhancement of 2,4-dinitrotoluene biodegradation by Burkholderia sp. in sand bioreactors using bacterial hemoglobin technology . Biodegradation . en . 15 . 3 . 161–171 . 10.1023/B:BIOD.0000026496.38594.b2 . 15228074 . 1572-9729.
  30. Kunkel . Stephanie A. . Pagilla . Krishna R. . Stark . Benjamin C. . 2015-08-01 . Engineering of Nitrosomonas europaea to express Vitreoscilla hemoglobin enhances oxygen uptake and conversion of ammonia to nitrite . AMB Express . 5 . 1 . 43 . 10.1186/s13568-015-0135-2 . free . 2191-0855 . 4522006 . 26231847.
  31. Arnaldos . Marina . Kunkel . Stephanie A. . Stark . Benjamin C. . Pagilla . Krishna R. . 2014-04-01 . Characterization of heme protein expressed by ammonia-oxidizing bacteria under low dissolved oxygen conditions . Applied Microbiology and Biotechnology . en . 98 . 7 . 3231–3239 . 10.1007/s00253-013-5400-1 . 24272370 . 1432-0614.
  32. Kaur . Ramandeep . Ahuja . Sandhya . Anand . Arvind . Singh . Balwinder . Stark . Benjamin. C. . Webster . Dale. A. . Dikshit . Kanak L. . 2008-10-15 . Functional implications of the proximal site hydrogen bonding network in Vitreoscilla hemoglobin (VHb): Role of Tyr95 (G5) and Tyr126 (H12) . FEBS Letters . en . 582 . 23–24 . 3494–3500 . 10.1016/j.febslet.2008.09.018 . 18804465 . 2008FEBSL.582.3494K . 0014-5793.
  33. Kim . Yongsoon . Webster . Dale A. . Stark . Benjamin C. . 2005 . Improvement of bioremediation by Pseudomonas and Burkholderia by mutants of the Vitreoscilla hemoglobin gene (vgb) integrated into their chromosomes . Journal of Industrial Microbiology & Biotechnology . 32 . 4 . 148–154 . 10.1007/s10295-005-0215-4 . 15806390 . 1367-5435.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "VHb (hemoglobin)".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.