Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp

Tarricone, C.; Galizzi, Alessandro; Coda, Alessandro; Ascenzi, Paolo; Bolognesi, M.

doi:10.1016/s0969-2126(97)00206-2

Cited by 133 publications

(163 citation statements)

References 66 publications

Supporting

Mentioning

156

Contrasting

Order By: Relevance

“…If oxyVHb interacted with cytochrome bo and transferred superoxide anion (one electron-reduced oxygen) to the cytochrome, this would obviate the need for a fourth electron-transferring metal (copper) in the binuclear center. An NADH-flavoprotein metVHb reductase that is present in Vitreoscilla and that copurifies with the VHb has been suggested to form a dissociable complex with structural/functional equivalence to other microbial flavohemoglobins (21). This flavoprotein could serve to re-reduce the ferric VHb generated by the donation of superoxide anion.…”

Section: Construction Of Peg202::vgb and Pjg4-5::cyo Bo Ubiquinolmentioning

confidence: 99%

Vitreoscilla Hemoglobin Binds to Subunit I of Cytochrome bo Ubiquinol Oxidases

Park

Kim

Howard

et al. 2002

Journal of Biological Chemistry

106

View full text Add to dashboard Cite

The bacterium, Vitreoscilla, can induce the synthesis of a homodimeric hemoglobin under hypoxic conditions. Expression of VHb in heterologous bacteria often enhances growth and increases yields of recombinant proteins and production of antibiotics, especially under oxygen-limiting conditions. There is evidence that VHb interacts with bacterial respiratory membranes and cytochrome bo proteoliposomes. We have examined whether there are binding sites for VHb on the cytochrome, using the yeast two-hybrid system with VHb as the bait and testing every Vitreoscilla cytochrome bo subunit as well as the soluble domains of subunits I and II. A significant interaction was observed only between VHb and intact subunit I. We further examined whether there are binding sites for VHb on cytochrome bo from Escherichia coli and Pseudomonas aeruginosa, two organisms in which stimulatory effects of VHb have been observed. Again, in both cases a significant interaction was observed only between VHb and subunit I. Because subunit I contains the binuclear center where oxygen is reduced to water, these data support the function proposed for VHb of providing oxygen directly to the terminal oxidase; it may also explain its positive effects in Vitreoscilla as well as in heterologous organisms.

show abstract

Section: Construction Of Peg202::vgb and Pjg4-5::cyo Bo Ubiquinolmentioning

confidence: 99%

Vitreoscilla Hemoglobin Binds to Subunit I of Cytochrome bo Ubiquinol Oxidases

Park

Kim

Howard

et al. 2002

Journal of Biological Chemistry

106

View full text Add to dashboard Cite

show abstract

“…Crystal structures of three group I trHbs (2,3) revealed that trHbs are clearly not just another variation on the motif of vertebrate myoglobin (Mb) and Hb. Neither are they similar to nonvertebrate Hbs, including the heme-containing domain of flavohemoglobins, nor to the plant symbiotic and nonsymbiotic Hbs (4)(5)(6)(7)(8)(9)(10). Major structural differences associated with known trHbs are an unprecedented 2-on-2 ␣-helical sandwich fold, resulting from striking editing of the classical 3-on-3 globin ␣-helical sandwich, and an extended hydrophobic tunnel͞cavity network linking the solvent space and the distal heme pocket (1)(2)(3).…”

mentioning

confidence: 99%

“…The different H-bond networks thus achievable may not only stabilize the bound O 2 but also modulate the positioning and dynamics of distal pocket residues that participate in the control of ligand access to the iron, ligand diffusion within the distal heme pocket, and ligand diffusion into and out of the distal heme pocket (1)(2)(3)(4)(5)(6)(7)(8)(9)(10).…”

mentioning

confidence: 99%

A TyrCD1/TrpG8 hydrogen bond network and a TyrB10—TyrCD1 covalent link shape the heme distal site of Mycobacterium tuberculosis hemoglobin O

Milani

Savard

Ouellet

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

109

158

View full text Add to dashboard Cite

Truncated hemoglobins (Hbs) are small hemoproteins, identified in microorganisms and in some plants, forming a separate cluster within the Hb superfamily. Two distantly related truncated Hbs, trHbN and trHbO, are expressed at different developmental stages in Mycobacterium tuberculosis. Sequence analysis shows that the two proteins share 18% amino acid identities and belong to different groups within the truncated Hb cluster. Although a specific defense role against nitrosative stress has been ascribed to trHbN (expressed during the Mycobacterium stationary phase), no clear functions have been recognized for trHbO, which is expressed throughout the Mycobacterium growth phase. The 2.1-Å crystal structure of M. tuberculosis cyano-met trHbO shows that the protein assembles in a compact dodecamer. Six of the dodecamer subunits are characterized by a double conformation for their CD regions and, most notably, by a covalent bond linking the phenolic O atom of TyrB10 to the aromatic ring of TyrCD1, in the heme distal cavity. All 12 subunits display a cyanide ion bound to the heme Fe atom, stabilized by a tight hydrogen-bonded network based on the (globin very rare) TyrCD1 and TrpG8 residues. The small apolar AlaE7 residue leaves room for ligand access to the heme distal site through the conventional ''E7 path,'' as proposed for myoglobin. Different from trHbN, where a 20-Å protein matrix tunnel is held to sustain ligand diffusion to an otherwise inaccessible heme distal site, the topologically related region in trHbO hosts two protein matrix cavities.T runcated hemoglobins (trHbs) are a class of small oxygenbinding hemoproteins, dispersed in eubacteria, cyanobacteria, protozoa, and plants, recently recognized as a separate cluster within the hemoglobin (Hb) superfamily. On the basis of amino acid sequence analysis, three phylogenetic groups (groups I, II, and III) have been identified within the trHb family; some organisms contain genes from more than one group, suggesting different functions for trHbs belonging to the diverse groups (1). Crystal structures of three group I trHbs (2, 3) revealed that trHbs are clearly not just another variation on the motif of vertebrate myoglobin (Mb) and Hb. Neither are they similar to nonvertebrate Hbs, including the heme-containing domain of flavohemoglobins, nor to the plant symbiotic and nonsymbiotic Hbs (4-10). Major structural differences associated with known trHbs are an unprecedented 2-on-2 ␣-helical sandwich fold, resulting from striking editing of the classical 3-on-3 globin ␣-helical sandwich, and an extended hydrophobic tunnel͞cavity network linking the solvent space and the distal heme pocket (1-3). Much smaller and topologically unrelated cavities, known by their ability to incorporate Xe atoms, have been found in Mb and interpreted as temporary ligand-docking sites (11,12). In trHbs, the positioning and size of the hydrophobic tunnel suggest important roles in controlling ligand access to the heme, in ligand storage, and͞or accumulation (1-3).An additional major diffe...

show abstract

“…We also examined the effects of amino acid substitutions at the highly conserved Tyr(B10) position on NOD activity, reduction, and ligand binding kinetics (7,24). Key differences between flavoHb and other Hbs are discussed in light of this specialized but perhaps ancient NO dioxygenation and detoxification function of hemoglobin.…”

mentioning

confidence: 99%

Steady-state and Transient Kinetics of Escherichia coli Nitric-oxide Dioxygenase (Flavohemoglobin)

Gardner

Martin

Gardner

et al. 2000

Journal of Biological Chemistry

155

166

View full text Add to dashboard Cite

The flavoHbs 1 belong to a 1.8 billion-year-old family of globin molecules that includes O 2 -binding Hbs and Mbs isolated from animals, plants, fungi, protozoa, bacteria, and worms (1-6). FlavoHbs have a unique two-domain structure containing linked Hb and reductase domains with extensive homology to the mammalian Hbs and metHb reductases (1, 7). Other Hbs appear to be co-expressed with associated metHb reductases (8). An O 2 transport or storage function, like that of the erythrocytic Hbs and muscle Mbs, has been suggested for some microbial and plant (flavo)Hbs (4, 9); however, other functions including the catalysis of oxidations have long seemed more likely (10 -12).Recently, we described an NO dioxygenase (NOD) produced by Escherichia coli that utilizes O 2 and NAD(P)H to convert NO to nitrate (Equation 1) and identified it as a flavoHb (13,14). Subsequent studies have shown that related bacterial and yeast flavoHbs display a similar NOD activity.A role for flavoHbs in NO detoxification is supported by the ability of flavoHbs to protect bacteria against NO or nitroso compounds (13, 14, 16 -18) and by their induction in bacteria exposed to NO, nitrate, nitrite, or nitroso compounds (13, 14, 17, 19 -22). However, the mechanism of NO detoxification, and thus the function of the flavoHbs, is obscured by the possibility of multiple reaction mechanisms involving NO. Other NO detoxifying activities for flavoHbs, including denitrosylation of nitrosothiols (17), NO reduction (17, 23), and NO sequestration (16, 23), have been offered to explain the protection flavoHbs afford to bacteria against NO and nitrosoglutathione. Thus, an understanding of the biological function(s) of the flavoHbs demands a greater knowledge of their various activities.In this report, steady-state, reduction, and ligand binding kinetics of the E. coli NOD (flavoHb) were measured in order to define its function and the mechanism of NO dioxygenation. We also examined the effects of amino acid substitutions at the highly conserved Tyr(B10) position on NOD activity, reduction, and ligand binding kinetics (7,24). Key differences between flavoHb and other Hbs are discussed in light of this specialized but perhaps ancient NO dioxygenation and detoxification function of hemoglobin. MATERIALS AND METHODSCells and Reagents-The flavoHb-deficient E. coli strain RB9060 (25) was generously provided by Alex Ninfa (University of Michigan). Plasmid pAlter containing the E. coli hmp gene was prepared as described previously (13). FAD, NADPH, and bovine hemin were purchased from Sigma. NADH, bovine liver catalase (260,000 units/ml), and deoxyribonuclease were obtained from Roche Molecular Biochemicals. Saturated NO was prepared as described previously (26). Saturated O 2 (1.14 mM) was prepared by vigorously scrubbing a solution of 50 mM potassium phosphate, pH 7.8, containing 0.1 mM EDTA (buffer A) at 25°C and atmospheric pressure with 99.993% O 2 (Praxair, Bethlehem, PA) in a rubber septum-sealed glass vial vented with a syringe needle. Manganese-containing...

show abstract

Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp

Cited by 133 publications

References 66 publications

Vitreoscilla Hemoglobin Binds to Subunit I of Cytochrome bo Ubiquinol Oxidases

Vitreoscilla Hemoglobin Binds to Subunit I of Cytochrome bo Ubiquinol Oxidases

A TyrCD1/TrpG8 hydrogen bond network and a TyrB10—TyrCD1 covalent link shape the heme distal site of Mycobacterium tuberculosis hemoglobin O

Steady-state and Transient Kinetics of Escherichia coli Nitric-oxide Dioxygenase (Flavohemoglobin)

Contact Info

Product

Resources

About