scholarly journals Architecture of the mycobacterial succinate dehydrogenase with a membrane-embedded Rieske FeS cluster

2021 ◽  
Vol 118 (15) ◽  
pp. e2022308118
Author(s):  
Xiaoting Zhou ◽  
Yan Gao ◽  
Weiwei Wang ◽  
Xiaolin Yang ◽  
Xiuna Yang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Succinate Dehydrogenase ◽  
Krebs Cycle ◽  
Water Soluble ◽  
Electron Transfer Mechanism ◽  
Complex Ii ◽  
Electron Transfer Pathway ◽  
Quinone Binding ◽  
Reduction Activity ◽  
Quinone Reduction

Complex II, also known as succinate dehydrogenase (SQR) or fumarate reductase (QFR), is an enzyme involved in both the Krebs cycle and oxidative phosphorylation. Mycobacterial Sdh1 has recently been identified as a new class of respiratory complex II (type F) but with an unknown electron transfer mechanism. Here, using cryoelectron microscopy, we have determined the structure of Mycobacterium smegmatis Sdh1 in the presence and absence of the substrate, ubiquinone-1, at 2.53-Å and 2.88-Å resolution, respectively. Sdh1 comprises three subunits, two that are water soluble, SdhA and SdhB, and one that is membrane spanning, SdhC. Within these subunits we identified a quinone-binding site and a rarely observed Rieske-type [2Fe-2S] cluster, the latter being embedded in the transmembrane region. A mutant, where two His ligands of the Rieske-type [2Fe-2S] were changed to alanine, abolished the quinone reduction activity of the Sdh1. Our structures allow the proposal of an electron transfer pathway that connects the substrate-binding and quinone-binding sites. Given the unique features of Sdh1 and its essential role in Mycobacteria, these structures will facilitate antituberculosis drug discovery efforts that specifically target this complex.

scholarly journals Electron-Transfer Pathways in the Heme and Quinone-Binding Domain of Complex II (Succinate Dehydrogenase)

Biochemistry ◽  
2014 ◽  
Vol 53 (10) ◽  
pp. 1637-1646 ◽  
Author(s):  
Robert F. Anderson ◽  
Sujata S. Shinde ◽  
Russ Hille ◽  
Richard A. Rothery ◽  
Joel H. Weiner ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Succinate Dehydrogenase ◽  
Binding Domain ◽  
Complex Ii ◽  
Quinone Binding ◽  
Electron Transfer Pathways

scholarly journals The Quinone Binding Site in Escherichia coli Succinate Dehydrogenase Is Required for Electron Transfer to the Heme b

2006 ◽  
Vol 281 (43) ◽  
pp. 32310-32317 ◽  
Author(s):  
Quang M. Tran ◽  
Richard A. Rothery ◽  
Elena Maklashina ◽  
Gary Cecchini ◽  
Joel H. Weiner
Keyword(s):  
Escherichia Coli ◽  
Electron Transfer ◽  
Succinate Dehydrogenase ◽  
Radical Intermediate ◽  
Electron Transfer Pathway ◽  
Potentiometric Titrations ◽  
Quinone Binding ◽  
Enzyme Turnover ◽  
Succinate:Ubiquinone Oxidoreductase

We have examined the role of the quinone-binding (QP) site of Escherichia coli succinate:ubiquinone oxidoreductase (succinate dehydrogenase) in heme reduction and reoxidation during enzyme turnover. The SdhCDAB electron transfer pathway leads from a cytosolically localized flavin adenine dinucleotide cofactor to a QP site located within the membrane-intrinsic domain of the enzyme. The QP site is sandwiched between the [3Fe-4S] cluster of the SdhB subunit and the heme b556 that is coordinated by His residues from the SdhC and SdhD subunits. The intercenter distances between the cluster, heme, and QP site are all within the theoretical 14 Å limit proposed for kinetically competent intercenter electron transfer. Using EPR spectroscopy, we have demonstrated that the QP site of SdhCDAB stabilized a ubisemiquinone radical intermediate during enzyme turnover. Potentiometric titrations indicate that this species has an Em,8 of ∼60 mV and a stability constant (KSTAB) of ∼1.0. Mutants of the following conserved QP site residues, SdhC-S27, SdhC-R31, and SdhD-D82, have severe consequences on enzyme function. Mutation of the conserved SdhD-Y83 suggested to hydrogen bond to the ubiquinone cofactor had a less severe but still significant effect on function. In addition to loss of overall catalysis, these mutants also affect the rate of succinate-dependent heme reduction, indicating that the QP site is an essential stepping stone on the electron transfer pathway from the [3Fe-4S] cluster to the heme. Furthermore, the mutations result in the elimination of EPR-visible ubisemiquinone during potentiometric titrations. Overall, these results demonstrate the importance of a functional, semiquinone-stabilizing QP site for the observation of rapid succinate-dependent heme reduction.

scholarly journals Succinate dehydrogenase (SDHx) mutations in pituitary tumors: could this be a new role for mitochondrial complex II and/or Krebs cycle defects?

2012 ◽  
Vol 19 (6) ◽  
pp. C33-C40 ◽  
Author(s):  
Paraskevi Xekouki ◽  
Constantine A Stratakis
Keyword(s):  
Thyroid Cancer ◽  
Succinate Dehydrogenase ◽  
Krebs Cycle ◽  
Pituitary Tumors ◽  
Tricarboxylic Acid ◽  
Genetic Defects ◽  
Disease Phenotype ◽  
Cowden Disease ◽  
Mitochondrial Complex ◽  
Complex Ii

Succinate dehydrogenase (SDH) or mitochondrial complex II is a multimeric enzyme that is bound to the inner membrane of mitochondria and has a dual role as it serves both as a critical step of the tricarboxylic acid or Krebs cycle and as a member of the respiratory chain that transfers electrons directly to the ubiquinone pool. Mutations in SDH subunits have been implicated in the formation of familial paragangliomas (PGLs) and/or pheochromocytomas (PHEOs) and in Carney–Stratakis syndrome. More recently, SDH defects were associated with predisposition to a Cowden disease phenotype, renal, and thyroid cancer. We recently described a kindred with the coexistence of familial PGLs and an aggressive GH-secreting pituitary adenoma, harboring anSDHDmutation. The pituitary tumor showed loss of heterozygosity at theSDHDlocus, indicating the possibility thatSDHD's loss was causatively linked to the development of the neoplasm. In total, 29 cases of pituitary adenomas presenting in association with PHEOs and/or extra-adrenal PGLs have been reported in the literature since 1952. Although a number of other genetic defects are possible in these cases, we speculate that the association of PHEOs and/or PGLs with pituitary tumors is a new syndromic association and a novel phenotype for SDH defects.

scholarly journals Electron transfer activity through the quinone-binding site of complex II (succinate: Quinone reductase)

2010 ◽  
Vol 1797 ◽  
pp. 111
Author(s):  
Gary Cecchini ◽  
Elena Maklashina ◽  
Sujata S. Shinde ◽  
Robert F. Anderson ◽  
Russ Hille
Keyword(s):  
Electron Transfer ◽  
Binding Site ◽  
Quinone Reductase ◽  
Complex Ii ◽  
Transfer Activity ◽  
Quinone Binding

The structure of Na+-translocating of NADH:ubiquinone oxidoreductase of Vibrio cholerae: implications on coupling between electron transfer and Na+ transport

2015 ◽  
Vol 396 (9-10) ◽  
pp. 1015-1030 ◽  
Author(s):  
Julia Steuber ◽  
Georg Vohl ◽  
Valentin Muras ◽  
Charlotte Toulouse ◽  
Björn Claußen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Cytoplasmic Membrane ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Effective Electron ◽  
X Ray ◽  
Electron Transfer Pathway ◽  
Quinone Reduction ◽  
Redox Centers

Abstract The Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) of Vibrio cholerae is a respiratory complex that couples the exergonic oxidation of NADH to the transport of Na+ across the cytoplasmic membrane. It is composed of six different subunits, NqrA, NqrB, NqrC, NqrD, NqrE, and NqrF, which harbor FAD, FMN, riboflavin, quinone, and two FeS centers as redox co-factors. We recently determined the X-ray structure of the entire Na+-NQR complex at 3.5-Å resolution and complemented the analysis by high-resolution structures of NqrA, NqrC, and NqrF. The position of flavin and FeS co-factors both at the cytoplasmic and the periplasmic side revealed an electron transfer pathway from cytoplasmic subunit NqrF across the membrane to the periplasmic NqrC, and via NqrB back to the quinone reduction site on cytoplasmic NqrA. A so far unknown Fe site located in the midst of membrane-embedded subunits NqrD and NqrE shuttles the electrons over the membrane. Some distances observed between redox centers appear to be too large for effective electron transfer and require conformational changes that are most likely involved in Na+ transport. Based on the structure, we propose a mechanism where redox induced conformational changes critically couple electron transfer to Na+ translocation from the cytoplasm to the periplasm through a channel in subunit NqrB.

scholarly journals Customized exogenous ferredoxin functions as an efficient electron carrier

2021 ◽  
Author(s):  
Zhan Song ◽  
Cancan Wei ◽  
Chao Li ◽  
Xin Gao ◽  
Shuhong Mao ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Protein Interactions ◽  
Reaction System ◽  
Protein Protein Interactions ◽  
Potential Measurement ◽  
Electron Carrier ◽  
Electron Transfer Pathway ◽  
Reduction Activity ◽  
Biological Electron Transfer

Ferredoxin (Fdx) is regarded as the main electron carrier in biological electron transfer and acts as an electron donor in metabolic pathways of many organisms. Here, we screened a self-sufficient P450-derived reductase PRF with promising NADPH reduction activity and 9OHAD production yield and proved the importance of [2Fe-2S] clusters of Fdx-containing oxidoreductase in transferring electrons in steroidal conversion. The truncated Fdx domain in all oxidoreductases, together with mutagenesis data, further elucidated the indispensable role of [2Fe-2S] clusters in the electron transfer process. By adding the independent plant-type Fdx to the reaction system, the AD conversion rate have been significantly improved. A novel efficient electron transfer pathway of PRF+Fdx+KshA in the reaction system rather than KshAB complex system was proposed based on analysis of protein-protein interactions and redox potential measurement. Adding free Fdx created a new conduit for electrons to travel from reductase to oxygenase. This electron transfer pathway provides new insight for the development of efficient exogenous Fdx as an electron carrier.

Photosensitized damage of protein by fluorinated diethoxyphosphorus(V)porphyrin

2013 ◽  
Vol 17 (01n02) ◽  
pp. 56-62 ◽  
Author(s):  
Kazutaka Hirakawa ◽  
Keito Azumi ◽  
Yoshinobu Nishimura ◽  
Tatsuo Arai ◽  
Yoshio Nosaka ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Human Serum Albumin ◽  
Serum Albumin ◽  
Singlet Oxygen ◽  
Human Serum ◽  
Transfer Mechanism ◽  
Water Soluble ◽  
Electron Transfer Mechanism ◽  
Oxygen Generation ◽  
Singlet Oxygen Generation

The effect of the axial ligand fluorination of the water-soluble P(V)porphyrin complex on photosensitized protein damage was examined. The activity of singlet oxygen generation by diethoxyP(V) porphyrin was slightly improved by the fluorination of the ethoxy chains. Absorption spectrum measurements demonstrated the binding interaction between the P(V)porphyrins and human serum albumin, a water-soluble protein. Photo-irradiated P(V)porphyrins damaged the amino acid residue of human serum albumin, resulting in the decrease of the fluorescence intensity from the tryptophan residue of human serum albumin. A singlet oxygen quencher, sodium azide, could not completely inhibit the damage of human serum albumin, suggesting that the electron transfer mechanism contributes to protein damage as does singlet oxygen generation. The decrease of the fluorescence lifetime of P(V)porphyrin by human serum albumin supported the electron transfer mechanism. The estimated contributions of the electron transfer mechanism are 0.57 and 0.44 for the fluorinated and non-fluorinated P(V)porphyrins, respectively. The total quantum yield of the protein photo-oxidation was slightly enhanced by this axial fluorination.

Guanine-specific DNA oxidation photosensitized by the tetraphenylporphyrin P(V) complex

2006 ◽  
Vol 10 (11) ◽  
pp. 1285-1292 ◽  
Author(s):  
Kazutaka Hirakawa ◽  
Shosuke Kawanishi ◽  
Hiroshi Segawa ◽  
Toru Hirano
Keyword(s):  
Dna Damage ◽  
Electron Transfer ◽  
High Performance ◽  
Near Infrared ◽  
Infrared Emission ◽  
Water Soluble ◽  
Electron Transfer Mechanism ◽  
Double Stranded Dna ◽  
Dna Photodamage ◽  
Water Soluble Porphyrin

Porphyrins have been studied as photosensitizers in photodynamic therapy. DNA is one of the most important targets of the sensitizer. In the present study, we have examined the photosensitized DNA damage caused by dihydroxo P ( V ) tetraphenylporphyrin ( P ( V ) TPP ), a cationic water-soluble porphyrin. P ( V ) TPP photosensitized guanine-specific damage to the DNA fragment. P ( V ) TPP induced severe photodamage to single-stranded rather than to double-stranded DNA. High performance liquid chromatography measurements confirmed the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-G), an oxidized product of 2'-deoxyguanosine, and showed that the content of 8-oxo-G in single-stranded DNA is larger than that in double-stranded DNA. The effects of reactive oxygen scavengers on DNA damage suggested the involvement of singlet oxygen (1 O 2). Photosensitized 1 O 2 formation was confirmed by near-infrared emission measurements. The results showed that 1 O 2 formation mainly contributes to the mechanism of DNA photodamage by P ( V ) TPP . Absorption spectrum measurements showed the interaction between P ( V ) TPP and DNA. This interaction is expected to enhance the 1 O 2-mediated DNA damage since the lifetime of 1 O 2 in a cell is very short. On the other hand, P ( V ) TPP induced DNA damage at the consecutive guanines in double-stranded DNA. Because the consecutive guanines act as a hole trap, this DNA-damaging pattern suggests the partial involvement of photo-induced electron transfer. The fluorescence of P ( V ) TPP was quenched by DNA, supporting the electron transfer mechanism. However, DNA damage by electron transfer was not a main mechanism possibly due to reverse electron transfer. In conclusion, P ( V ) TPP binds to DNA and induces guanine-specific, photo-oxidation mainly via 1 O 2 generation.

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