Ligand Binding in the Ferric and Ferrous States of <i>Paramecium</i> Hemoglobin

Das, Tapan K.; Weber, Roy E.; Dewilde, Sylvia; Wittenberg, Jonathan B.; Wittenberg, Beatrice A.; Yamauchi, Kiyoshi; Hauwaert, M L Van; Moëns, Luc; Rousseau, Denis L.

doi:10.1021/bi001681d

Cited by 65 publications

(70 citation statements)

References 67 publications

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“…The Fe-His stretching frequency of Ctb (226 cm -1 shown in Fig. 5) is similar to results obtained for other trHbs, lying between 220 and 232 cm -1 (13,25,34,35,37). In mammalian Hb or Mb, the imidazole ring of the proximal histidine is in an eclipsed orientation with respect to the pyrrole nitrogen atoms of the porphyrin, in contrast to a staggered orientation in the trHbs (36).…”

Section: Group III Trhbssupporting

confidence: 82%

“…This H-bonding interaction is not present in any of the trHbs with known structures, consistent with their relatively lower ν Fe-His . Taken together, these observations suggest that the proximal histidine ligand of Ctb has neutral character and has its imidazole ring in a staggered position with respect to the pyrrole nitrogen atoms of the porphyrin ring (13,25,31,(34)(35)(36)(37)(38).…”

Section: Group III Trhbsmentioning

confidence: 97%

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Purification and Spectroscopic Characterization of Ctb, a Group III Truncated Hemoglobin Implicated in Oxygen Metabolism in the Food-Borne Pathogen Campylobacter jejuni

et al. 2006

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Campylobacter jejuni is a foodborne bacterial pathogen that possesses two distinct hemoglobins, encoded by the ctb and cgb genes. The former codes for a truncated hemoglobin (Ctb) in group III, an assemblage of uncharacterized globins in diverse clinically-and technologically-significant bacteria. Here, we show that Ctb purifies as a monomeric, predominantly oxygenated species. Optical spectra of ferric, ferrous, O 2 -and CO-bound forms resemble those of other hemoglobins. However, resonance Raman analysis shows Ctb to have an atypical ν Fe-CO stretching mode at 514 cm -1 , compared to the other truncated hemoglobins that have been characterized so far. This implies unique roles in ligand stabilisation for TyrB10, HisE7 and TrpG8, residues highly conserved within group III truncated hemoglobins. Since C. jejuni is a microaerophile, and a ctb mutant exhibits O 2 -dependent growth defects, one of the hypothesised roles of Ctb is in the detoxification, sequestration or transfer of O 2 The midpoint potential (E h ) of Ctb was found to be −33 mV, but no evidence was obtained in vitro to support the hypothesis that Ctb is reducible by NADH or NADPH. This truncated hemoglobin may function in the facilitation of O 2 transfer to one of the terminal oxidases of C. jejuni or instead facilitate O 2 transfer to Cgb for NO detoxification.In the past three decades, our understanding of hemoglobins has grown to recognise new classes of proteins in addition to the classical vertebrate α-and β-globins, myoglobin and the symbiotic Hbs of leguminous plants. These 'new' globins -some of which may actually be amongst the oldest, or ancestral, globins in a phylogenetic context (1) -include the non-symbiotic plant Hbs, chimeric flavohemoglobins, and the trHbs. Globins may be classified functionally -into those that detoxify NO and those that are involved in O 2 transfer or detoxification -or structurally into three categories (2). The first structural category contains flavoHbs that possess a C-terminal ferredoxin-NADP + reductase-like domain and an N-terminal globin domain; bacterial (3,4) and yeast (5) examples function in the enzymic removal of NO to produce nitrate (6,7). The second category contains single domain Hbs that are very similar to the N-terminal domain of the flavoHbs; however, their functions appear more varied than those of the flavoHbs. As an example, Vgb, found in the obligate aerobe Vitreoscilla, is believed to function in the facilitation of O 2 transfer to cytochrome bo' (8), whereas the C.

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Section: Group III Trhbssupporting

confidence: 82%

Section: Group III Trhbsmentioning

confidence: 97%

Purification and Spectroscopic Characterization of Ctb, a Group III Truncated Hemoglobin Implicated in Oxygen Metabolism in the Food-Borne Pathogen Campylobacter jejuni

et al. 2006

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“…The absorption spectra observed for the carbonmonoxy, oxy, and deoxy forms of the hemoglobin (Fig. 1) are similar to those found for other hemoglobins, including the truncated hemoglobins from Nostoc (22) and Paramecium (11).…”

supporting

confidence: 73%

Hemoglobin in Frankia , a Nitrogen-Fixing Actinomycete

Tjepkema

Cashon

Beckwith

et al. 2002

Appl Environ Microbiol

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“…CO may interact with a distal His in myoglobin and hemoglobin, but does not bind similarly to distal amino acids in CooA (48) and P. caudatum Hb (49). Therefore, CO is unlikely to interact directly with distal amino acids in Ec DOS.…”

Section: Fig 6 Ft Ir Spectra Of Co Complexes Of the Wild Type (--)mentioning

confidence: 96%

Binding of Oxygen and Carbon Monoxide to a Heme-regulated Phosphodiesterase from Escherichia coli

Taguchi

Matsui

Igarashi

et al. 2004

Journal of Biological Chemistry

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The heme-regulated phosphodiesterase, Ec DOS, is a redox sensor that uses the heme in its PAS domain to regulate catalysis. The rate of O 2 association (k on ) with full-length Ec DOS is extremely slow at 0. 0019 The phosphodiesterase (PDE) 1 from Escherichia coli, Ec DOS, is composed of an N-terminal heme-bound PAS domain and a C-terminal PDE catalytic domain (1). The basic physicochemical characteristics and function of this enzyme have been partially elucidated by our group and that of Kitagawa et al. (1,2). PDE activity is dependent on the redox state of Ec DOS in that the enzyme is active only when the heme is in the Fe(II) state. Changes in the redox state of the heme bound to the N-terminal PAS domain may induce a subtle conformational change, which intramolecularly transmits signals to the C-terminal PDE domain to initiate and/or regulate catalysis. Ec DOS therefore constitutes a novel class of heme enzymes designated "heme-based sensors" (3-5). These include proteins such as FixL (6, 7), CooA (8, 9), sGC (10, 11), and Hem-AT (12, 13). In these enzymes, association or dissociation of the exogenous axial ligand (O 2 , CO, or NO) from the heme iron leads to protein conformational changes, which in turn transmit signals to other domains to regulate catalysis or binding to DNA. The Ec DOS signal transducing mechanism appears to be unique, since changes in the redox state of the PAS domain, rather than iron coordination chemistry, are responsible for signal transduction (1). However, in other words, signal transduction triggered by ligand binding (CO and NO) is common to Ec DOS and FixL, based on the finding that CO or NO binding abolishes catalysis by Ec DOS (1).The physicochemical properties of the isolated heme-bound PAS domain of Ec DOS were initially characterized by GillesGonzales and colleagues (14). The kinetics of exogenous axial ligand binding to the heme protein and associated equilibrium constants provide useful information on the structure and characteristics of the heme distal site and ligand access channel (16 -19). It is important to study O 2 and CO binding, particularly to full-length Ec DOS, to clarify whether the enzyme is a direct O 2 sensor. These analyses would also be useful in elucidating the structure of the heme distal site and ligand access channel and their relation to the signal transduction mechanism. Based on the amino acid sequence alignment and crystal structure of a similar PAS enzyme, FixL (7,20,21), Met-95 is suggested as a heme axial ligand trans to His-77.In the present study, we report rate and equilibrium constants for O 2 and CO binding to the full-length enzyme in the Fe(II) state, isolated heme-bound PAS domain, and Met-95 * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.‡ To whom correspondence should be addressed: Institute of Multidisciplinary Research for Advanced Materials, Tohok...

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Ligand Binding in the Ferric and Ferrous States of Paramecium Hemoglobin

Cited by 65 publications

References 67 publications

Purification and Spectroscopic Characterization of Ctb, a Group III Truncated Hemoglobin Implicated in Oxygen Metabolism in the Food-Borne Pathogen Campylobacter jejuni

Purification and Spectroscopic Characterization of Ctb, a Group III Truncated Hemoglobin Implicated in Oxygen Metabolism in the Food-Borne Pathogen Campylobacter jejuni

Hemoglobin in Frankia , a Nitrogen-Fixing Actinomycete

Binding of Oxygen and Carbon Monoxide to a Heme-regulated Phosphodiesterase from Escherichia coli

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