Dimeric and tetrameric hemoglobins from the mollusc Scapharca inaequivalvis

Chiancone, Emilia; Vecchini, Paola; Verzili, Daniela; Ascoli, Franca; Antonini, Eraldo

doi:10.1016/0022-2836(81)90270-9

Cited by 152 publications

(96 citation statements)

References 18 publications

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“…The occurrence of cooperative homodimeric Mb's and Hb's in invertebrates [3,6,7] opens the question whether they might all be representatives of an ancestral class of hemoproteins with a similar primitive hemeAbbreviations: Mb, Myoglobin; Hb, Hemoglobin; N. mutabilis Mb, Nassa mutabilh' homodimerie myoglobin; S. inaequivalvls Hb, Scapharca inaequivalvi~ homodimgrie hemoglobiP. heme interaction mechanism(s) in spite of their different location and physiological role.…”

Section: Introductionmentioning

confidence: 99%

Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis Kinetic and spectroscopic evidence

et al. 1992

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CO binding kinetics to the homodimeric myoglobin (Mb) from Nassa mut#bilis has been investigated between pH 1.9 and 7.0. Protonation of the proximal imidazole at low pH ('~ 3.0) and the consequent cleavage of the HisFgNE2-Fe proximal bond brings about a ~ 20-fold increase of the second.order rate constant for CO binding. This process displays a pK~ = 4.0 ± 0.2, significantly higher than that observed in all other deoxygenated hemoproteins investigated up to now. Such a feature underlies a decreased energy for the HisFgNE2-Fe proximal bond in the unliganded form and it also appears supported by resonance Raman spectroscopy in the low frequency region of the Fe(II) deoxygenated hemoprotein. Further, the pH-rate profile of N, mutabilia' Mb, like that of the homodimerie hemoglobin (Hb) from Scapharca inaequh,alvis (Coletta, M., Boffi, A., Ascenzl, P., Brunori, M. and Chianeone, E. (1990) J. Biol. Chem. 265, 4828-4830), can be described only by assumin~ a concerted proton.linked transition with n = 1.8 __. 0. i. Such a characteristic suggests, also on the basis of the amino acid sequenc~ homology between N. mutabilis Mb and S. inaequivah,is Hb in the region forming the subanit interface, that the interaction mechanism is similar for the two homodimerie proteins, and drastically different from that operative in otimr hemoproteins.

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Section: Introductionmentioning

confidence: 99%

Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis Kinetic and spectroscopic evidence

et al. 1992

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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.…”

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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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“…Blood clams, such as T. granosa, Scapharca inaequivalvis, Anadara trapezia, and S. broughtonii, contain 2 types of hemoglobins that cooperatively bind oxygen (Chiancone et al, 1981;Royer et al, 1985). The major hemoglobin component, HbII, is formed by two polypeptide chains (A and B) that associate to form an A 2 B 2 heterotetramer.…”

Section: Introductionmentioning

confidence: 99%

Structure and immune expression analysis of hemoglobin genes from the blood clam Tegillarca granosa

Bao

Wang²,

Zhang³

2013

Genet. Mol. Res.

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ABSTRACT. Hemoglobin (Hb) is the major protein component of erythrocytes in animals with red blood, although it can serve additional functions beyond the transport of oxygen. The blood clam (Tegillarca granosa) is one of the few mollusks that has Hb, although the structure and function of molluskan Hbs remain unclear. We characterized two unique and highly compartmentalized blood clam hemoglobin genes, Tg-HbIIA and Tg-HbIIB, at the molecular level. The full-length cDNA of Tg-HbIIA was 731 bp with a 450-bp open reading frame encoding 150 amino acids; that of Tg-HbIIB was 698 bp, with a 456-bp open reading frame encoding 152 amino acids. Their intronic regions were amplified by PCR. The two genes showed the typical 2 intron/3 exon organization found in T. granosa. The 3-D structures of the three blood clam Tg-Hbs were predicted using the SWISS-MODEL Protein Modeling Server, and a phylogenetic analysis was conducted to investigate its evolution. As quantified by qRT-PCR, the expression levels of Tg-HbIIA and Tg-HbIIB were significantly upregulated upon challenge by Vibrio

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Dimeric and tetrameric hemoglobins from the mollusc Scapharca inaequivalvis

Cited by 152 publications

References 18 publications

Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis Kinetic and spectroscopic evidence

Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis Kinetic and spectroscopic evidence

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

Structure and immune expression analysis of hemoglobin genes from the blood clam Tegillarca granosa

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