Stereodynamic properties of the cooperative homodimeric Scapharca inaequivalvis hemoglobin studied through optical absorption spectroscopy and ligand rebinding kinetics

Boffi, Alberto; Verzili, Daniela; Chiancone, Emilia; Leone, Maurizio; Cupane, Antonio; Militello, Valeria; Vitrano, Eugenio; Cordone, Lorenzo; Yu, Weiming; Iorio, Ernesto E. Di

doi:10.1016/s0006-3495(94)80645-9

Cited by 31 publications

(36 citation statements)

References 30 publications

(49 reference statements)

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“…On the other hand, the ferrous form of the protein shows substantial stability over a wide pH range. These observations suggest that Scapharca hemoglobin has a unique heme structure that undergoes substantial redox-dependent rearrangements that stabilize the Fe-proximal histidine bond in the functional deoxy form of the protein but not in the ferric form.The homodimeric hemoglobin (HbI) 1 isolated from arcid clam Scapharca inaequivalvis possesses unique structural features (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Although HbI has a low sequence homology with tetrameric mammalian hemoglobins (Hb), it has a conserved globin fold.…”

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confidence: 99%

“…The homodimeric hemoglobin (HbI) 1 isolated from arcid clam Scapharca inaequivalvis possesses unique structural features (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Although HbI has a low sequence homology with tetrameric mammalian hemoglobins (Hb), it has a conserved globin fold.…”

mentioning

confidence: 99%

“…Although a wealth of structural and functional information is available on the ferrous deoxy and ligand-bound forms of HbI (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), little is known about the oxidized form (1). The heme structure in the ferric form undergoes a spin transition that is dependent on pH and salt concentration (17,18).…”

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confidence: 99%

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Hydroxide Rather Than Histidine Is Coordinated to the Heme in Five-coordinate Ferric Scapharca inaequivalvisHemoglobin

Das¹,

Boffi²,

Chiancone³

et al. 1999

Journal of Biological Chemistry

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The ferric form of the homodimeric Scapharca hemoglobin undergoes a pH-dependent spin transition of the heme iron. The transition can also be modulated by the presence of salt. From our earlier studies it was shown that three distinct species are populated in the pH range 6 -9. At acidic pH, a low-spin six-coordinate structure predominates. At neutral and at alkaline pHs, in addition to a small population of a hexacoordinate high-spin species, a pentacoordinate species is significantly populated. Isotope difference spectra clearly show that the heme group in the latter species has a hydroxide ligand and thereby is not coordinated by the proximal histidine. The stretching frequency of the Fe-OH moiety is 578 cm ؊1 and shifts to 553 cm ؊1 in H 2 18 O, as would be expected for a Fe-OH unit. On the other hand, the ferrous form of the protein shows substantial stability over a wide pH range. These observations suggest that Scapharca hemoglobin has a unique heme structure that undergoes substantial redox-dependent rearrangements that stabilize the Fe-proximal histidine bond in the functional deoxy form of the protein but not in the ferric form.The homodimeric hemoglobin (HbI) 1 isolated from arcid clam Scapharca inaequivalvis possesses unique structural features (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Although HbI has a low sequence homology with tetrameric mammalian hemoglobins (Hb), it has a conserved globin fold. It displays a unique structural basis for cooperative ligand binding in that the two hemes face each other across the intersubunit contact and are able to communicate directly through their propionate groups (2,4,15,16). As a consequence of this unusual structural linkage, cooperativity is accompanied by major tertiary changes in the heme environment with only minor rearrangements of the quaternary structure, in contrast to mammalian Hbs (2, 13). The subunit interface in HbI is formed mostly by the helices E and F, which are solventexposed in tetrameric mammalian Hbs.Although a wealth of structural and functional information is available on the ferrous deoxy and ligand-bound forms of HbI (2-14), little is known about the oxidized form (1). The heme structure in the ferric form undergoes a spin transition that is dependent on pH and salt concentration (17,18). From our earlier studies by optical and resonance Raman spectroscopy, it was shown that a mixture of three distinct species are populated in the pH range 6 -9 (17, 18). The formation of a sixcoordinate low-spin heme is favored at acidic pH and high ionic strength and is accompanied by the reversible dissociation of the HbI dimer into monomers. This species is likely to be formed by coordination of the distal histidine to the heme (in addition to the proximal histidine) as shown by EPR studies (18). At neutral pH values, a dimeric pentacoordinate species appears and becomes the dominant form at alkaline pH and low salt. A population of dimeric six-coordinate high-spin heme exists over the entire 6 -9 pH-range and in both low and high salt. Thi...

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Hydroxide Rather Than Histidine Is Coordinated to the Heme in Five-coordinate Ferric Scapharca inaequivalvisHemoglobin

Das¹,

Boffi²,

Chiancone³

et al. 1999

Journal of Biological Chemistry

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“…Some broadening of the Soret band was observed in the presence of bare ZnO NPs. Transition from the near Gaussian to the non‐Gaussian form of the Soret band (inset of Figure ), indicated that the iron atom affected the in‐plane towards the out‐of‐heme plane and additionally produced conformational homogeneity inside the heme‐porphyrin system . The use of C ZnO = 0.0.5 mg/ml within the ZnO NP–BSA bioconjugate shown in Figure (d) gave rise to a peak at c .…”

Section: Resultsmentioning

confidence: 94%

Microscopic and spectroscopic study of the corona formation and unfolding of human haemoglobin in presence of ZnO nanoparticles

Bhunia

Saha

Kamilya³

2019

Luminescence

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The interaction of zinc oxide nanoparticles (ZnO NPs) with human haemoglobin (Hb) is studied for the biologically safe application of ZnO NPs in the human body. The Hb corona is formed around the ZnO nanoparticles, directly observed from highresolution transmission electron microscopy (HRTEM) images. Hb formed 'hard corona' on the surface of ZnO NPs from an exponential association mechanism over a very short duration, as well as unfolding of Hb that occurred over a long lifetime.Dynamic light scattering measurements demonstrated that the ZnO NPs were completely covered by Hb with shell thickness of c. 6 nm that formed a 'hard corona'.Zeta potential measurements represented that the ZnO NPs were fully covered by Hb molecules using an exponential association mechanism. Tryptophans (TRY), as well as heme-porphyrin moieties of Hb, are the major binding sites for ZnO NPs.The nature of the interaction between ZnO NPs and Hb was analysed from the fluorescence quenching of TRYs. Electrostatic interaction, along with the hydrophobic interaction between ZnO NPs and Hb, is responsible for the conformational change in Hb due to increase in the percentage of β-sheets together with a decrease in αhelices.

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“…The limited success of intracellular mammalian Hbs has also motivated researchers to investigate the naturally extracellular hemoglobins of invertebrates (aka Erythrocruorins or Ecs). Ecs from a variety of organisms have been studied, including annelids, mollusks, insects, snails, and many more . Overall, the most thoroughly investigated Ecs are from the annelids Lumbricus terrestris and Arenicola marina, which are both huge macromolecular complexes (MW ∼3.6 MDa).…”

Section: Introductionmentioning

confidence: 99%

Direct comparison of oligochaete erythrocruorins as potential blood substitutes

Zimmerman

DiIusto

Dienes

et al. 2017

Bioengineering & Transla Med

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While many blood substitutes are based on mammalian hemoglobins (e.g., human hemoglobin, HbA), the naturally extracellular hemoglobins of invertebrates (a.k.a. erythrocruorins, Ecs) are intriguing alternative oxygen carriers. Specifically, the erythrocruorin of Lumbricus terrestris has been shown to effectively deliver oxygen in mice and rats without the negative side effects observed with HbA. In this study, the properties of six oligochaete Ecs (Lumbricus terrestris, Eisenia hortensis, Eisenia fetida, Eisenia veneta, Eudrilus eugeniae, and Amynthas gracilis) were compared in vitro to identify the most promising blood substitute candidate(s). Several metrics were used to compare the Ecs, including their oxidation rates, dissociation at physiological pH, thermal stability, and oxygen transport characteristics. Overall, the Ecs of Lumbricus terrestris (LtEc) and Eisenia fetida (EfEc) were identified as promising candidates, since they demonstrated high thermal and oligomeric stability, while also exhibiting relatively low oxidation rates. Interestingly, the O2 affinity of LtEc (P 50 = 26.25 mmHg at 37 °C) was also observed to be uniquely lower than EfEc and all of the other Ecs (P 50 = 9.29–13.62 mmHg). Subsequent alignment of the primary sequences of LtEc and EfEc revealed several significant amino acid substitutions within the D subunit interfaces that may be responsible for this significant change in O2 affinity. Nonetheless, these results show that LtEc and EfEc are promising potential blood substitutes that are resistant to oxidation and denaturation, but additional experiments will need to be conducted to determine their safety, efficacy, and the effects of their disparate oxygen affinities in vivo.

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Stereodynamic properties of the cooperative homodimeric Scapharca inaequivalvis hemoglobin studied through optical absorption spectroscopy and ligand rebinding kinetics

Cited by 31 publications

References 30 publications

Hydroxide Rather Than Histidine Is Coordinated to the Heme in Five-coordinate Ferric Scapharca inaequivalvisHemoglobin

Hydroxide Rather Than Histidine Is Coordinated to the Heme in Five-coordinate Ferric Scapharca inaequivalvisHemoglobin

Microscopic and spectroscopic study of the corona formation and unfolding of human haemoglobin in presence of ZnO nanoparticles

Direct comparison of oligochaete erythrocruorins as potential blood substitutes

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