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

Coletta, Massimo; Ascenzi, Paolo; Smulevich, Giulietta; Mantini, Anna R.; Gaudio, Rosanna del; Piscopo, Marina; Geraci, Giuseppe

doi:10.1016/0014-5793(92)80375-q

Cited by 11 publications

(16 citation statements)

References 16 publications

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“…1). This second protonation is reminiscent of that described previously in human adult Hb (10), as well as in other monomeric and dimeric hemoproteins (9,29,30), and it may be referred to the protonation of the N ⑀ atom of the His F8 imidazole ring, and the consequent cleavage (or severe weakening) of the proximal His F8 -Fe bond. This interpretation seems supported by the observation that the transient absorption spectrum of unliganded C. kumu Hb in the visible region displays features characteristic of a tetracoordinated heme (see Fig.…”

Section: Ph Dependence Of Subunit Heterogeneity In Fish Hbsupporting

confidence: 55%

Proton-linked Subunit Kinetic Heterogeneity for Carbon Monoxide Binding to Hemoglobin from Chelidonichthys kumu

Coletta

Ascenzi²,

D’Avino

et al. 1996

Journal of Biological Chemistry

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Section: Ph Dependence Of Subunit Heterogeneity In Fish Hbsupporting

confidence: 55%

Proton-linked Subunit Kinetic Heterogeneity for Carbon Monoxide Binding to Hemoglobin from Chelidonichthys kumu

Coletta

Ascenzi²,

D’Avino

et al. 1996

Journal of Biological Chemistry

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“…An additional piece of information may come from the pH dependence of CO binding to both Hs-Nb and Mt-Nb, which does not show any enhancement over the 2.2-7.0 pH range ( Figure 5A). This behavior is drastically different from what observed in most of the other hemoproteins, wherefore at pH < 5.0 a relevant increase of the CO binding rate constant is observed with variable pK a values [56,[61][62][63][64][65][66][67]. This feature, which was attributed to the cleavage (or severe weakening) of the heme-Fe-His proximal bond in the unliganded form, as demonstrated by the spectroscopic features, is characterized by the blue-shift of the absorption spectrum in the Soret region and the appearance of two peaks at 525 and 565 nm [56,61,62].…”

Section: Heme-proteincontrasting

confidence: 89%

“…Actually, the much slower CO binding rate constants for Hs-Nb and Mt-Nb (Table 1), which display an activation free energy (∆G ‡ = 43.7 kJ/mol for Hs-Nb and 45.0 kJ/mol for Mt-Nb) much higher than that of Ec-Mb (∆G ‡ = 39.2 kJ/mol) and Pc-Mb (∆G ‡ = 39.7 kJ/mol), might stem from crowding of H 2 O molecules in the distal side of the heme pocket, as observed from X-ray structures of Fe(III) Nbs [26], which would raise the free energy barrier for ligand binding to the heme's Fe atom. However, an additional contribution might arise from a higher energy barrier for the in-plane movement of the unliganded heme-Fe-His proximal bond to bind CO [56,[61][62][63][64][65][66][67]. The strain, exerted on the proximal His-Fe(II) bond by this movement, may be due to the clustering of amino acid side chains in the proximal side of the heme pocket, which might be also responsible for the resistance of the proximal bond even at very low pH values ( Figure 5).…”

Section: Discussionmentioning

confidence: 99%

Mycobacterial and Human Ferrous Nitrobindins: Spectroscopic and Reactivity Properties

Masi

Pesce

et al. 2021

IJMS

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Structural and functional properties of ferrous Mycobacterium tuberculosis (Mt-Nb) and human (Hs-Nb) nitrobindins (Nbs) were investigated. At pH 7.0 and 25.0 °C, the unliganded Fe(II) species is penta-coordinated and unlike most other hemoproteins no pH-dependence of its coordination was detected over the pH range between 2.2 and 7.0. Further, despite a very open distal side of the heme pocket (as also indicated by the vanishingly small geminate recombination of CO for both Nbs), which exposes the heme pocket to the bulk solvent, their reactivity toward ligands, such as CO and NO, is significantly slower than in most hemoproteins, envisaging either a proximal barrier for ligand binding and/or crowding of H2O molecules in the distal side of the heme pocket which impairs ligand binding to the heme Fe-atom. On the other hand, liganded species display already at pH 7.0 and 25 °C a severe weakening (in the case of CO) and a cleavage (in the case of NO) of the proximal Fe-His bond, suggesting that the ligand-linked movement of the Fe(II) atom onto the heme plane brings about a marked lengthening of the proximal Fe-imidazole bond, eventually leading to its rupture. This structural evidence is accompanied by a marked enhancement of both ligands dissociation rate constants. As a whole, these data clearly indicate that structural–functional relationships in Nbs strongly differ from what observed in mammalian and truncated hemoproteins, suggesting that Nbs play a functional role clearly distinct from other eukaryotic and prokaryotic hemoproteins.

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“…A very strong ⌬H, larger than that of mammalian Hbs (22), was measured in A. orianae Hb at pH 8.0, in the absence and presence of chloride and ATP. However, lowering the pH to 7.0 brought about a dramatic decrease of the oxygen-binding enthalpy, which became almost zero in the presence of effectors (Table II).…”

Section: Resultsmentioning

confidence: 99%

The Hemoglobins of the Antarctic Fishes Artedidraco orianae and Pogonophryne scotti

Tamburrini

Romano

Carratore

et al. 1998

Journal of Biological Chemistry

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The oxygen-transport system of two species of Antarctic fishes belonging to the family Artedidraconidae, Artedidraco orianae and Pogonophryne scotti, was thoroughly investigated. The complete amino acid sequence of the ␣ and ␤ chains of the single hemoglobins of the two species was established. The oxygen-binding properties were also investigated, and were found not to differ significantly from those shown by blood, intact erythrocytes, and unstripped hemolysates. Both hemoglobins have unusually high oxygen affinity and display a relatively small Bohr effect; the Root effect is elicited only by organophosphates and is also reduced. Remarkably, the Hill coefficient is close to one in the whole pH range, indicating absence of cooperative oxygen binding which, in A. orianae hemoglobin, could be ascribed to the subunit heterogeneity shown upon oxygen dissociation. In comparison with the other families of the suborder Notothenioidei, the oxygen-transport system of these two species of Artedidraconidae has unique characteristics, which raise interesting questions on the mode of function of a multisubunit molecule and the relationship with cold adaptation.During adaptation to low temperatures, Antarctic fishes have acquired special hematological features which clearly differentiate them from fishes of temperate and tropical climates. The hematocrit and hemoglobin (Hb) 1 concentration are highly reduced in the blood of Antarctic fishes (1-3), as well as the number of Hb components. At the extreme of such evolution, the 15 species of the family Channichthyidae are characterized by lack of Hb (4).The hematological peculiarities of Antarctic teleosts prompted an investigation on the molecular structure and ligand binding properties of hemoglobins (Hbs) from these organisms, in order to characterize the adaptation of the oxygentransport mechanism at the molecular level. We focused our interest on the suborder Notothenioidei, largely endemic and confined south of the Antarctic Polar Front. The suborder includes six families with 120 species, 95 of which are Antarctic (5, 6): Bovichtidae, Nototheniidae, Harpagiferidae, Artedidraconidae, Bathydraconidae, and Channichthyidae (in fact, the families might be seven, since recent evidence (7) suggests that Bovichtidae should be grouped into Pseudaphritidae and Bovichtidae).Notothenioids generally have a single major Hb (Hb 1), often accompanied by a minor component (Hb 2), accounting for approximately 95 and 5% of the total, respectively (8 -10). A cathodal Hb (Hb C) is present in trace amounts, except in Trematomus newnesi, of the family Nototheniidae, in which Hb C is approximately 25-30% of the total (11).In this study, the oxygen-transport system of species of the family Artedidraconidae, which comprises 24 of the 80 redblooded Antarctic species of the suborder Notothenioidei so far identified (5, 6), was thoroughly investigated for the first time. Artedidraconids are benthic fish, have a wide depth distribution, and are largely confined in the Antarctic continental shelf and...

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

Cited by 11 publications

References 16 publications

Proton-linked Subunit Kinetic Heterogeneity for Carbon Monoxide Binding to Hemoglobin from Chelidonichthys kumu

Proton-linked Subunit Kinetic Heterogeneity for Carbon Monoxide Binding to Hemoglobin from Chelidonichthys kumu

Mycobacterial and Human Ferrous Nitrobindins: Spectroscopic and Reactivity Properties

The Hemoglobins of the Antarctic Fishes Artedidraco orianae and Pogonophryne scotti

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