Spectroscopic identification of the axial ligands of cytochrome <i>b</i><sub>560</sub> in bovine heart succinate‐ubiquinone reductase

Crouse, Brian R.; Yu, Linda; Johnson, Michael K.

doi:10.1016/0014-5793(95)00522-b

Cited by 24 publications

(13 citation statements)

References 31 publications

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“…The g z ϭ 2.92 peak may be due to a dramatic modification of the environment of the heme responsible for the g z ϭ 3.76 peak of the NarGHI holoenzyme, or it may be due to an altered conformation of the heme responsible for the g z ϭ 3.15 signal. EPR signals with a low-field component (g z ) at g ϭ 2.92 have been observed for conformationally modified (or "relaxed") membrane-bound b-type cytochromes (29,30). Overall, the EPR spectra of membranes enriched in NarI demonstrate that the correct insertion of both b-type hemes requires the presence of the NarGH dimer.…”

Section: Resultsmentioning

confidence: 89%

“…Attempts to rationalize such large g values within a number of membrane-bound b-type cytochromes have relied upon the assumption of distortion at the heme center controlled by the orientation of the imidazole rings (29,32). Palmer (27) has proposed that if the two imidazole-ring planes of the ligating histidines are gradually rotated from a parallel orientation, which gives a g z of about 3.0, toward a perpendicular orientation, the g z increases, and the g y and g x components of the EPR signal become progressively smaller.…”

Section: Figmentioning

confidence: 99%

“…In the latter case, heme insertion in the different membrane-bound subunits can only occur after the complete formation of the cytochrome bd oxidase complex. In the case of the cytochrome b 560 in bovine heart succinate-ubiquinone reductase, the pronounced changes in EPR properties that accompany isolation of the cytochrome b 560 are attributed to perturbation of the orientation of the imidazole rings of the heme bis-histidine ligands (29). In the case of the B. subtilis cytochrome b 558 , the hemes in the whole complex II and in the isolated cytochrome subunit are not in the same environment as judged by differences in the optical absorption and EPR spectra (32).…”

Section: Figmentioning

confidence: 99%

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Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

Magalon

Lemesle-Meunier²,

Rothery³

et al. 1997

Journal of Biological Chemistry

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Nitrate reductase A (NarGHI) 1 is the predominant respiratory complex in the membrane of Escherichia coli when the cells are grown under anaerobic conditions in the presence of nitrate. This complex catalyzes electron transfer from quinol to nitrate coupled to proton release into the periplasm and the generation of a concomitant transmembrane proton electrochemical potential (1). NarGHI is a complex of three nonidentical subunits, NarG (150 kDa), NarH (60 kDa), and NarI (25 kDa), in the ratio of 1:1:1 as predicted by the operon organization. This complex is arranged in two catalytic domains: the NarGH subunits constitute the cytoplasmic domain and NarI the membrane anchor domain (2, 3). The NarGH domain contains four [Fe-S] centers (4, 5) and a molybdenum cofactor which is the site of nitrate reduction by the enzyme (6). The NarI subunit (cytochrome b nr ) is a diheme b-type cytochrome required for attachment of the cytoplasmic domain to the inner side of the cytoplasmic membrane (3) and it mediates electron transfer from the membrane quinol pool (menaquinol or ubiquinol) to the molybdenum cofactor (2, 7). Optical redox titrations demonstrate the presence of two hemes in NarGHI with midpoint potentials (E m,7 values) of ϩ17 and ϩ122 mV (8).Of the well characterized membrane-intrinsic cytochromes b, the hemes are found to have bis-histidine ligation (9 -11), and it is very likely that this is also the case with the hemes of NarGHI. The hydropathy plot 2 and sequence analysis of NarI using the "positive inside" rule of von Heijne (12) leads to a topological model in which five transmembrane ␣-helical segments (helices I-V) are arranged with a periplasmic N terminus and a cytoplasmic C terminus (13). Five His residues are present in predicted transmembrane segments, at positions 56, 66, 74, 187, and 205. Sequence alignment of all known sequences of NarI from various bacterial membrane-bound nitrate reductases (4, 13, 14) reveals only four totally conserved histidines (His-56,His-66 in helix II and His-187,His-205 in helix V) as potential heme ligands, thereby excluding His-74 within helix II in heme ligation (13). Overall, this strongly suggests ligation of each heme by two histidine residues (13). Because of the different spacing of the conserved histidines on helix II (9 residues) and V (17 residues), the hemes probably lie in two planes with different angles relative to the plane of the membrane. Recently, an alternative model for heme ligation in NarI has been proposed by van der Oost et al. (15) on the basis of subunit stoichiometry and sequence analysis of various b-type cytochromes. This model predicts that the hemes are sandwiched in a NarI dimer and ligated only by His-187 and His-205 of helix V of each NarI subunit. Genetic procedures are, therefore, required for identifying the heme ligands and to distinguish the different models.In the present work, we have used site-directed mutagenesis, as well as optical and EPR spectroscopies, to test whether the two conserved histidine residues within helix II (Hi...

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Section: Resultsmentioning

confidence: 89%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

Magalon

Lemesle-Meunier²,

Rothery³

et al. 1997

Journal of Biological Chemistry

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“…The single heme in mammalian and E. coli SQR and the two hemes in B. subtilis SQR have bis-histidine axial ligation as demonstrated by EPR spectroscopy combined with lowtemperature near-infrared MCD spectroscopy [13][14][15]. The ligand histidine residues have been identified in the primary sequence of the B. subtilis and E. coli SQR anchor polypeptides by site directed mutagenesis analysis [12,16,17].…”

Section: The Cytoehrome B Componentmentioning

confidence: 99%

A structural moDAl for the membrane‐integral domain of succinate:quinone oxidoreductases

Hägerhäll¹,

Hederstedt²

1996

FEBS Letters

123

102

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Many succinate:quinone oxidoreductases in bacteria and mitochondria, i.e. succinate:quinone reductases and fumarate reductases, contain in the membrane anchor a cytochrome b whose structure and function is poorly understood. Based on biochemical data and polypeptide sequence information, we show that the anchors in different organisms are related despite an apparent diversity in polypeptide and heine composition. A general structural model for the membrane-integral domain of the anchors is proposed. It is an antiparallel four-helix bundle with a novel arrangement of hexa-coordinated protoheme IX. The structure can be applied to a larger group of membraneintegral cytochromes of b-type and has evolutionary and functional implications.

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“…Perpendicular imidazole rings provide the most axial environment which leads to very intense NIR-MCD charge transfer bands (Ae values up to 560 M ~ • cm -t at 4.2 K and 5 T) and low field g-values approaching 4.0. b-Type cytochromes with properties approaching this extreme are found in membrane bound environments in which the cytochrome bridges across two membrane spanning helices, e.g. in the cytochrome bc~ complex [24] and in the membrane anchor subunits of succinate dehydrogenases [25,26]. The majority bis-histidine ligated low spin ferric heme species in cytochrome b558 is clearly in well-defined environment somewhere between the extremes of parallel and perpendicular imidazole rings.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic identification of the heme axial ligation of cytochrome b₅₅₈ in the NADPH oxidase of porcine neutrophils

1995

FEBS Letters

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The combination of electron paramagnetic resonance (EPR), near-infrared magnetic circular dichroism (NIR-MCD) and resonance Raman (RR) spectroscopies at cryogenic temperatures has been used to identify the axial heine ligation of the low spin cytochrome bs5 s component of NADPH oxidase from porcine blood neutrophils. The EPR and NIR-MCD results indicate the presence of two distinct forms in frozen solution; one with a low field g-value at 3.23 and porphyrin(Tr)-to-Fe(lII) charge transfer maximum at 1660 nm and the other a low field g-value at 3.00 and porphyrin(r0-to-Fe(IlI ) charge transfer maximum at 1510 nm. On the basis of these properties and the RR studies, both are attributed to forms of cytochrome bsss with bis-histidine axial ligation. The origin of the observed heterogeneity, the location and identity of the specific histidines involved in ligating the heine, and the role of the heine prosthetic group in 02 production are discussed in light of these results.

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Spectroscopic identification of the axial ligands of cytochrome b₅₆₀ in bovine heart succinate‐ubiquinone reductase

Cited by 24 publications

References 31 publications

Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

A structural moDAl for the membrane‐integral domain of succinate:quinone oxidoreductases

Spectroscopic identification of the heme axial ligation of cytochrome b₅₅₈ in the NADPH oxidase of porcine neutrophils

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Spectroscopic identification of the axial ligands of cytochrome b560 in bovine heart succinate‐ubiquinone reductase

Cited by 24 publications

References 31 publications

Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

Heme Axial Ligation by the Highly Conserved His Residues in Helix II of Cytochrome b (NarI) of Escherichia coliNitrate Reductase A (NarGHI)

A structural moDAl for the membrane‐integral domain of succinate:quinone oxidoreductases

Spectroscopic identification of the heme axial ligation of cytochrome b558 in the NADPH oxidase of porcine neutrophils

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Spectroscopic identification of the axial ligands of cytochrome b₅₆₀ in bovine heart succinate‐ubiquinone reductase

Spectroscopic identification of the heme axial ligation of cytochrome b₅₅₈ in the NADPH oxidase of porcine neutrophils