Crystal Structure of Soybean Ferric Leghaemoglobin a Nicotinate at a Resolution of 3.3Ǻ

Ollis, David L.; Appleby, Cyril A.; Colman, P.M.; Cutten, A. E.; Guss, J.M.; Venkatappa, M. P.; Freeman, H. C.

doi:10.1071/ch9830451

Cited by 50 publications

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“…The fact that Lb has a larger distal heme cavity than Mb has been reported previously for both soybean Lb a (Ollis et al, 1983) and lupin Lb II (Arutyunyan, Kuranova, Vainshtein & Steigemann, 1980;Arutyunyan, Kuranova, Tovbis et al, 1980;Harutyunyan et al, 1995). B, C, E, G and H helices all align closely.…”

Section: The Heme Group and Heme Cavitymentioning

confidence: 77%

“…The structure of soybean Lb a nicotinate was solved by the method of multiple isomorphous replacement (MIR) at 3.3 ]k resolution, as described previously (Ollis et al, 1983). We here report the refinement at 2.3 ~ resolution.…”

Section: Methodsmentioning

confidence: 99%

“…The seven helices (A-C, E-H) common to all globin structures account for approximately 75% of the amino acids. The refinement of the structure and a rigorous application of the Kabsch & Sander (1983) criteria have resulted in several minor changes from the original helix assignment of Ollis et al (1983) (Fig. 2).…”

Section: Description Of the Moleculementioning

confidence: 99%

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Structure of Ferric Soybean LeghemoglobinaNicotinate at 2.3 Å Resolution

Ellis¹,

Appleby²,

Guss³

et al. 1997

Acta Cryst D

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Soybean leghemoglobin a is a small (16 kDa) protein facilitating the transport of Oz to respiring N2-fixing bacteria at low free-O2 tension. The crystal structure of soybean ferric leghemoglobin a nicotinate has been refined at 2.3 A resolution. The final R factor is 15.8% for 6877 reflections between 6.0 and 2.3 ~. The structure of soybean leghemoglobin a (143 residues) is closely similar to that of lupin leghemoglobin II (153 residues), the proteins having 82 identical residues when the sequences are aligned. The new structure provides support for the conclusion that the unique properties of leghemoglobin arise principally from a heme pocket considerably larger and more flexible than that of myoglobin, a strongly ruffled heme group, and a proximal histidine orientation more favourable to ligand binding.

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Section: The Heme Group and Heme Cavitymentioning

confidence: 77%

Section: Methodsmentioning

confidence: 99%

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Structure of Ferric Soybean LeghemoglobinaNicotinate at 2.3 Å Resolution

Ellis¹,

Appleby²,

Guss³

et al. 1997

Acta Cryst D

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“…Several environmental factors have been shown to influence the sign of Soret CD spectra of heme proteins. Thus, the mirror image Soret CD spectra of AOS and BLC can likely be attributed to differences in the size or hydrophobicity of their active site heme environments (42,43). The Soret CD sign difference could also be explained as a result of flipping of the heme by 180°about an in-plane axis (44).…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Coral Allene Oxide Synthase Active Site with UV−Visible Absorption, Magnetic Circular Dichroism, and Electron Paramagnetic Resonance Spectroscopy: Evidence for Tyrosinate Ligation to the Ferric Enzyme Heme Iron

et al. 2001

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Coral allene oxide synthase (AOS), a hemoprotein with weak sequence homology to catalase, is the N-terminal domain of a naturally occurring fusion protein with an 8R-lipoxygenase. AOS converts 8R-hydroperoxyeicosatetraenoic acid to the corresponding allene oxide. The UV-visible absorption and magnetic circular dichroism spectra of ferric AOS and of its cyanide and azide complexes, and the electron paramagnetic resonance spectra of native AOS (high-spin, g ) 6.56, 5.22, 2.00) and of its cyanide adduct (low-spin, g ) 2.86, 2.24, 1.60) closely resemble the corresponding spectra of bovine liver catalase (BLC). These results provide strong evidence for tyrosinate ligation to the heme iron of AOS as has been established for catalases. On the other hand, the positive circular dichroism bands in the Soret region for all three derivatives of ferric AOS are almost the mirror image of those in catalase. In addition, the cyanide affinity of native AOS (K d ) 10 mM at pH 7) is about 3 orders of magnitude lower than that of BLC. Thus, while these results conclusively support a common tyrosinate-ligated heme in AOS as in catalase, significant differences exist in the interaction between their respective heme prosthetic groups and protein environments, and in the access of small molecules to the heme iron.Interest in the enzymology underlying the high prostaglandin content of the Caribbean sea whip coral, Plexaura homomalla, has been the impetus for several biochemical investigations. Arachidonic acid is metabolized in extracts of P. homomalla and related corals by a lipoxygenase (LOX) 1 pathway that appeared initially to relate to the production of cyclopentenone prostaglandins (1, 2). An 8R-lipoxygenase converts arachidonic acid to 8R-hydroperoxyeicosatetraenoic acid (8R-HPETE), and the fatty acid hydroperoxide is then enzymatically dehydrated to an allene oxide, an epoxide with a propensity to cyclize to cyclopentenone derivatives. Brash et al., in 1997, isolated the cDNA of an 8R-lipoxygenase from P. homomalla and found it to occur with an extra sequence in the open reading frame that encodes the allene oxide synthase (AOS) (3). This natural fusion protein in coral consists of a LOX C-terminal domain (79 kDa) and an AOS N-terminal domain (43 kDa). The truncated (AOS) construct catalyzes an identical reaction to the AOS domain in the fusion protein, converting 8R-HPETE solely to the allene oxide. The truncated construct exhibits very high turnover number (1400/s) (4), although, due to the weaker expression of the fusion protein in E. coli, the comparable values for the fusion protein remain to be determined. 2 Although allene oxide has not proven to be an intermediate in the prostaglandin synthesis pathway (5), it may be linked to prostanoid type products such as clavulones and punaglandins of other corals (2,6,7). Allene oxides are very unstable epoxides; they readily hydrolyze into ketols, cyclopentenones, and other rearrangement products (8-10).The production of allene oxides from fatty acid hydroperoxides also ...

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“…Leghemoglobin (LHb), a symbiotic hemoglobin, is a monomeric heme protein originally identified in soybean root nodules and has been studied extensively (5,6). Because of its high affinity for oxygen, LHb makes less oxygen available, enhancing the nitrogen fixation process.…”

Section: Introductionmentioning

confidence: 99%

Iron Bioavailability of Hemoglobin from Soy Root Nodules Using a Caco-2 Cell Culture Model

Proulx

Reddy

2006

J. Agric. Food Chem.

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Heme iron has been identified in many plant sourcesmost commonly in the root nodules of leguminous plants, such as soy. Our objective was to test the effectiveness of soy root nodule (SRN) and purified soy hemoglobin (LHb) in improving iron bioavailability using an in vitro Caco-2 cell model, with ferritin response as the bioavailability index. We assessed bioavailability of iron from LHb (either partially purified (LHbA) or purified (LHbD)) with and without food matrix and compared it with that from bovine hemoglobin (BHb), ferrous sulfate (FeSO4), or SRN. Bioavailability of each treatment was normalized to 100% of the FeSO4 treatment. When iron sources were tested alone (100 ug iron/mL), ferritin synthesis by LHbD and BHb were 19% (P > 0.05) and 113% (P < 0.001) higher than FeSO4, respectively. However, when iron sources were used for fortification of maize tortillas (50 ppm), LHbA and BHb showed similar bioavailability, being 27% (P < 0.05) and 33% (P < 0.05) higher than FeSO4. Heat treatment had no effect on heme iron but had a significant reduction on FeSO4 bioavailability. Adding heme (LHbA) iron with nonheme (FeSO4) had no enhancement on nonheme iron absorption. Our data suggest that heme iron from plant sources may be a novel value-added product that can provide highly bioavailable iron as a food fortificant. KeywordsIron bioavailability; heme iron; soy root nodules; leghemoglobin Heme iron has been identified in many plant sourcessmost commonly in the root nodules of leguminous plants, such as soy. Our objective was to test the effectiveness of soy root nodule (SRN) and purified soy hemoglobin (LHb) in improving iron bioavailability using an in vitro Caco-2 cell model, with ferritin response as the bioavailability index. We assessed bioavailability of iron from LHb (either partially purified (LHb A ) or purified (LHb D )) with and without food matrix and compared it with that from bovine hemoglobin (BHb), ferrous sulfate (FeSO 4 ), or SRN. Bioavailability of each treatment was normalized to 100% of the FeSO 4 treatment. When iron sources were tested alone (100 ug iron/mL), ferritin synthesis by LHb D and BHb were 19% (P > 0.05) and 113% (P < 0.001) higher than FeSO 4 , respectively. However, when iron sources were used for fortification of maize tortillas (50 ppm), LHb A and BHb showed similar bioavailability, being 27% (P < 0.05) and 33% (P < 0.05) higher than FeSO 4 . Heat treatment had no effect on heme iron but had a significant reduction on FeSO 4 bioavailability. Adding heme (LHb A ) iron with nonheme (FeSO 4 ) had no enhancement on nonheme iron absorption. Our data suggest that heme iron from plant sources may be a novel valueadded product that can provide highly bioavailable iron as a food fortificant.

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Crystal Structure of Soybean Ferric Leghaemoglobin a Nicotinate at a Resolution of 3.3Ǻ

Cited by 50 publications

References 0 publications

Structure of Ferric Soybean LeghemoglobinaNicotinate at 2.3 Å Resolution

Structure of Ferric Soybean LeghemoglobinaNicotinate at 2.3 Å Resolution

Characterization of the Coral Allene Oxide Synthase Active Site with UV−Visible Absorption, Magnetic Circular Dichroism, and Electron Paramagnetic Resonance Spectroscopy: Evidence for Tyrosinate Ligation to the Ferric Enzyme Heme Iron

Iron Bioavailability of Hemoglobin from Soy Root Nodules Using a Caco-2 Cell Culture Model

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