1
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Yuan Z, Ouyang P, Gu K, Rehman T, Zhang T, Yin Z, Fu H, Lin J, He C, Shu G, Liang X, Yuan Z, Song X, Li L, Zou Y, Yin L. The antibacterial mechanism of oridonin against methicillin-resistant Staphylococcus aureus (MRSA). PHARMACEUTICAL BIOLOGY 2019; 57:710-716. [PMID: 31622118 PMCID: PMC8871620 DOI: 10.1080/13880209.2019.1674342] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 08/22/2019] [Accepted: 09/22/2019] [Indexed: 05/29/2023]
Abstract
Context: Methicillin-resistant Staphylococcus aureus (MRSA) is a very harmful bacterium. Oridonin, a component in Rabdosia rubescens (Hemsl.) Hara (Lamiaceae), is widely used against bacterial infections in China. Objective: We evaluated oridonin effects on MRSA cell membrane and wall, protein metabolism, lactate dehydrogenase (LDH), DNA and microscopic structure. Materials and methods: Broth microdilution and flat colony counting methods were used to measure oridonin minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against USA300 strain. Electrical conductivity and DNA exosmosis were analysed to study oridonin effects (128 μg/mL) on cell membrane and wall for 0, 1, 2, 4 and 6 h. Sodium dodecyl sulphate polyacrylamide gel electrophoresis was used to detect effects on soluble protein synthesis after 6, 10 and 16 h. LDH activity was examined with an enzyme-linked immunosorbent assay. Effects of oridonin on USA300 DNA were investigated with DAPI staining. Morphological changes in MRSA following oridonin treatment were determined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results: Oridonin MIC and MBC values against USA300 were 64 and 512 μg/mL, respectively. The conductivity and DNA exosmosis level of oridonin-treated USA300 improved by 3.20±0.84% and increased by 58.63 ± 1.78 μg/mL, respectively. LDH and soluble protein levels decreased by 30.85±7.69% and 27.51 ± 1.39%, respectively. A decrease in fluorescence intensity was reported with time. Oridonin affected the morphology of USA300. Conclusions: Oridonin antibacterial mechanism was related to changes in cell membrane and cell wall permeability, disturbance in protein and DNA metabolism, and influence on bacterial morphology. Thus, oridonin may help in treating MRSA infection.
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Affiliation(s)
- Zhongwei Yuan
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Ping Ouyang
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Kexin Gu
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Tayyab Rehman
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Tianyi Zhang
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Zhongqiong Yin
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Hualin Fu
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Juchun Lin
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Changliang He
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Gang Shu
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Xiaoxia Liang
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Zhixiang Yuan
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Xu Song
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Lixia Li
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Yuanfeng Zou
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
| | - Lizi Yin
- College of Veterinary Medicine, Sichuan Agriculture University, Chengdu, China
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 560] [Impact Index Per Article: 56.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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3
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Hsieh YC, Chia TS, Fun HK, Chen CJ. Crystal structure of dimeric flavodoxin from Desulfovibrio gigas suggests a potential binding region for the electron-transferring partner. Int J Mol Sci 2013; 14:1667-83. [PMID: 23322018 PMCID: PMC3565340 DOI: 10.3390/ijms14011667] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 12/03/2012] [Accepted: 12/25/2012] [Indexed: 11/16/2022] Open
Abstract
Flavodoxins, which exist widely in microorganisms, have been found in various pathways with multiple physiological functions. The flavodoxin (Fld) containing the cofactor flavin mononucleotide (FMN) from sulfur-reducing bacteria Desulfovibrio gigas (D. gigas) is a short-chain enzyme that comprises 146 residues with a molecular mass of 15 kDa and plays important roles in the electron-transfer chain. To investigate its structure, we purified this Fld directly from anaerobically grown D. gigas cells. The crystal structure of Fld, determined at resolution 1.3 Å, is a dimer with two FMN packing in an orientation head to head at a distance of 17 Å, which generates a long and connected negatively charged region. Two loops, Thr59-Asp63 and Asp95-Tyr100, are located in the negatively charged region and between two FMN, and are structurally dynamic. An analysis of each monomer shows that the structure of Fld is in a semiquinone state; the positions of FMN and the surrounding residues in the active site deviate. The crystal structure of Fld from D. gigas agrees with a dimeric form in the solution state. The dimerization area, dynamic characteristics and structure variations between monomers enable us to identify a possible binding area for its functional partners.
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Affiliation(s)
- Yin-Cheng Hsieh
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan; E-Mail:
| | - Tze Shyang Chia
- X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia; E-Mails: (T.S.C.); (H.-K.F.)
| | - Hoong-Kun Fun
- X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia; E-Mails: (T.S.C.); (H.-K.F.)
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; E-Mail:
| | - Chun-Jung Chen
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan; E-Mail:
- Department of Physics, National Tsing Hua University, Hsinchu 30043, Taiwan
- Institute of Biotechnology, National Cheng Kung University, Tainan City 70101, Taiwan
- University Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan City 70101, Taiwan
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +886-3-5780281 (ext. 7330); Fax: +886-3-5783813
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4
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Abstract
This review is concerned specifically with the structures and biosynthesis of hemes in E. coli and serovar Typhimurium. However, inasmuch as all tetrapyrroles share a common biosynthetic pathway, much of the material covered here is applicable to tetrapyrrole biosynthesis in other organisms. Conversely, much of the available information about tetrapyrrole biosynthesis has been gained from studies of other organisms, such as plants, algae, cyanobacteria, and anoxygenic phototrophs, which synthesize large quantities of these compounds. This information is applicable to E. coli and serovar Typhimurium. Hemes play important roles as enzyme prosthetic groups in mineral nutrition, redox metabolism, and gas-and redox-modulated signal transduction. The biosynthetic steps from the earliest universal precursor, 5-aminolevulinic acid (ALA), to protoporphyrin IX-based hemes constitute the major, common portion of the pathway, and other steps leading to specific groups of products can be considered branches off the main axis. Porphobilinogen (PBG) synthase (PBGS; also known as ALA dehydratase) catalyzes the asymmetric condensation of two ALA molecules to form PBG, with the release of two molecules of H2O. Protoporphyrinogen IX oxidase (PPX) catalyzes the removal of six electrons from the tetrapyrrole macrocycle to form protoporphyrin IX in the last biosynthetic step that is common to hemes and chlorophylls. Several lines of evidence converge to support a regulatory model in which the cellular level of available or free protoheme controls the rate of heme synthesis at the level of the first step unique to heme synthesis, the formation of GSA by the action of GTR.
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5
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Kobayashi M, Saito T, Takahashi K, Wang ZY, Nozawa T. Electronic Properties and Thermal Stability of Soluble Redox Proteins from a Thermophilic Purple Sulfur Photosynthetic Bacterium,Thermochromatium tepidum. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2005. [DOI: 10.1246/bcsj.78.2164] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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6
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Niu S, Wang XB, Nichols JA, Wang LS, Ichiye T. Combined Quantum Chemistry and Photoelectron Spectroscopy Study of the Electronic Structure and Reduction Potentials of Rubredoxin Redox Site Analogues. J Phys Chem A 2003. [DOI: 10.1021/jp034316f] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shuqiang Niu
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Xue-Bin Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Jeffrey A. Nichols
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Lai-Sheng Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Toshiko Ichiye
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
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7
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Davidson VL, Sun D. Lysozyme-osmotic shock methods for localization of periplasmic redox proteins in bacteria. Methods Enzymol 2002; 353:121-30. [PMID: 12078488 DOI: 10.1016/s0076-6879(02)53042-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Victor L Davidson
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA
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8
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Fan C, Wagner G, Li G. Effect of dimethyl sulfoxide on the electron transfer reactivity of hemoglobin. Bioelectrochemistry 2001; 54:49-51. [PMID: 11506974 DOI: 10.1016/s0302-4598(01)00107-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hemoglobin, after being treated with dimethyl sulfoxide, exhibits a direct electrochemical response at a pyrolytic graphite electrode. The apparent standard potential (E degrees ') of hemoglobin is -0.119 V (vs. NHE). Meanwhile, since no electrochemical mediator is required for its direct electrochemistry, this work provides a convenient way to perform electrochemical research on this protein.
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Affiliation(s)
- C Fan
- Department of Biochemistry and National Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
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9
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Kaderbhai MA, Ugochukwu CC, Lamb DC, Kelly SL. Targeting of active human cytochrome P4501A1 (CYP1A1) to the periplasmic space of Escherichia coli. Biochem Biophys Res Commun 2000; 279:803-7. [PMID: 11162432 DOI: 10.1006/bbrc.2000.4001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Native human cytochrome P4501A1 (CYP1A1) was appended at its amino terminus to the secretory signal of Escherichia coli alkaline phosphatase. The chimeric P450 construct was placed under the transcriptional control of the native phoA promoter in a prokaryotic expression vector. Induction of the hemoprotein by heterologous expression in E. coli following growth in a phosphate-limited medium resulted in abundant synthesis of recombinant CYP1A1 as detected by reduced CO-difference spectra. Furthermore, the signal-appended CYP1A1 was translocated across the bacterial inner membrane by the sec-dependent pathway and processed to yield authentic, heme-incorporated P450 within the periplasmic space. In vitro and whole-cell metabolic activity studies showed that the periplasmically-located CYP1A1 competently catalysed NADPH-dependent benzo[a]pyrene 3-hydroxylation and 7-ethoxyresorufin O-deethylation. The means to localise cytochromes P450 in the periplasm offers an ability to produce high levels of protein, attributable to the less hostile nature of the compartment, and therein the enzymes for posttranslational assembly of heme with the translocated protein.
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Affiliation(s)
- M A Kaderbhai
- AberBiocentre, Institute of Biological Sciences, Edward Llwyd Building, Aberystwyth, Wales, SY23 3DA, United Kingdom
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10
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Zhao D, Hutton HM, Gooley PR, MacKenzie NE, Cusanovich MA. Redox-related conformational changes in Rhodobacter capsulatus cytochrome c2. Protein Sci 2000; 9:1828-37. [PMID: 11045628 PMCID: PMC2144708 DOI: 10.1110/ps.9.9.1828] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
WEFT-NOESY and transfer WEFT-NOESY NMR spectra were used to determine the heme proton assignments for Rhodobacter capsulatus ferricytochrome c2. The Fermi contact and pseudo-contact contributions to the paramagnetic effect of the unpaired electron in the oxidized state were evaluated for the heme and ligand protons. The chemical shift assignments for the 1H and 15N NMR spectra were obtained by a combination of 1H-1H and 1H-15N two-dimensional NMR spectroscopy. The short-range nuclear Overhauser effect (NOE) data are consistent with the view that the secondary structure for the oxidized state of this protein closely approximates that of the reduced form, but with redox-related conformational changes between the two redox states. To understand the decrease in stability of the oxidized state of this cytochrome c2 compared to the reduced form, the structural difference between the two redox states were analyzed by the differences in the NOE intensities, pseudo-contact shifts and the hydrogen-deuterium exchange rates of the amide protons. We find that the major difference between redox states, although subtle, involve heme protein interactions, orientation of the heme ligands, differences in hydrogen bond networks and, possible alterations in the position of some internal water molecules. Thus, it appears that the general destabilization of cytochrome c2, which occurs on oxidation, is consistent with the alteration of hydrogen bonds that result in changes in the internal dynamics of the protein.
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Affiliation(s)
- D Zhao
- Department of Pharmacology & Toxicology, College of Pharmacy, University of Arizona, Tucson 85721, USA
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11
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Mayburd AL, Tan Y, Kassner RJ. Complex formation between Chromatium vinosum ferric cytochrome c' and bromophenol blue. Arch Biochem Biophys 2000; 378:40-4. [PMID: 10871042 DOI: 10.1006/abbi.2000.1783] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An unusual complex has been observed between the common electrophoresis tracer bromophenol blue (BPB) and the cytochrome c' from Chromatium vinosum during polyacrylamide gel electrophoresis. Complex formation results in a shift and increase in the intensity of the visible absorption band of BPB. Differential spectrophotometric titration of BPB with cytochrome c' indicates that one BPB binds to each of the two subunits of cytochrome c' with a binding constant of 4.2(0.5) x 10(5). The absence of a significant effect of ionic strength on the binding constant and the effect of Triton X-100 on the spectrum of BPB suggest that hydrophobic interactions are important to binding. An analysis of the structure of C. vinosum cytochrome c' shows the presence of a surface hydrophobic patch which may participate in the binding interaction. Many of the hydrophobic amino acids in the patch are well conserved by type among all known sequences of cytochrome c' and are found in loop elements of the 3D structure, suggesting a functional basis for conservation. It is proposed that the binding of BPB may mimic a relevant interaction involving the cytochrome c' biological function.
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Affiliation(s)
- A L Mayburd
- Department of Chemistry, University of Illinois at Chicago, 60607, USA
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12
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Sticht H, Rösch P. The structure of iron-sulfur proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1998; 70:95-136. [PMID: 9785959 DOI: 10.1016/s0079-6107(98)00027-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ferredoxins are a group of iron-sulfur proteins for which a wealth of structural and mutational data have recently become available. Previously unknown structures of ferredoxins which are adapted to halophilic, acidophilic or hyperthermophilic environments and new cysteine patterns for cluster ligation and non-cysteine cluster ligation have been described. Site-directed mutagenesis experiments have given insight into factors that influence the geometry, stability, redox potential, electronic properties and electron-transfer reactivity of iron-sulfur clusters.
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Affiliation(s)
- H Sticht
- Lehrstuhl für Struktur und Chemie der Biopolymere, Universität Bayreuth, Germany.
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13
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Schlag EW, Lin SH, Weinkauf R, Rentzepis PM. Dynamical principles in biological processes. Proc Natl Acad Sci U S A 1998; 95:1358-62. [PMID: 9465019 PMCID: PMC19004 DOI: 10.1073/pnas.95.4.1358] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The purpose of this paper is to propose certain dynamical principles in biological systems, which can be used to explain the effectiveness of charge transfer or excitation transfer in biological systems. Some of these systems are accessible experimentally.
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Affiliation(s)
- E W Schlag
- Institute for Physical and Theoretical Chemistry, Technical University of Munich, D-86748 Garching, Germany
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14
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Battistuzzi G, Borsari M, Dallari D, Lancellotti I, Sola M. Anion binding to mitochondrial cytochromes c studied through electrochemistry. Effects of the neutralization of surface charges on the redox potential. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 241:208-14. [PMID: 8898908 DOI: 10.1111/j.1432-1033.1996.0208t.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The redox potential of horse and bovine heart cytochromes c determined through cyclic voltammetry is exploited to probe for anion-protein interactions, using a Debye-Hückel-based model. In parallel, protein charge neutralization resulting from specific anion binding allows monitoring for surface-charge/E(o) relationships. This approach shows that a number of anions, most of which are of biological relevance, namely CI-, HPO(2-)4, HCO3-, NO3, SO(2-)4, CIO4-, citrate3- and oxalate2-, bind specifically to the protein surface, often in a sequential manner as a result of the presence of multiple sites with different affinities. The binding stoichiometries of the various anions toward a given cytochrome are in general different. Chloride and phosphate appear to bind to a greater extent to both proteins as compared to the other anions. Differences in binding specificity toward the two cytochromes, although highly sequence-related, are observed for a few anions. The data are discussed comparatively in terms of electrostatic and geometric properties of the anions and by reference to the proposed location and amino acid composition of the anion binding sites, when available. Specific binding of this large set of anions bearing different charges allows the electrostatic effect on Eo due to neutralization of net positive protein surface charge(s) to be monitored. (J)H NMR indeed indicates the absence of significant salt-induced structural perturbations, hence the above change in Eo is predominantly electrostatic in origin. A systematic study of protein surface-charge/Eo relationships using this approach is unprecedented. Values of 15-25 mV (extrapolated at zero ionic strength) are obtained for the decrease in Eo due to neutralization of one positive surface charge, which are of the same order of magnitude as previous estimates obtained with either mutation or chemical modification of surface lysines. The effects of the anion-induced decrease of net positive charge on Eo persist also at a relatively high ionic strength and add to the general effects related to the charge shielding of the protein as a whole due to the surrounding ionic atmosphere: hence the ionic strength dependence of the rate of electron transfer between cytochromes c and redox partners could also involve salt-induced changes in the driving force.
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Affiliation(s)
- G Battistuzzi
- Department of Chemistry, University of Modena, Italy
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15
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Czjzek M, Guerlesquin F, Bruschi M, Haser R. Crystal structure of a dimeric octaheme cytochrome c3 (M(r) 26,000) from Desulfovibrio desulfuricans Norway. Structure 1996; 4:395-404. [PMID: 8740362 DOI: 10.1016/s0969-2126(96)00045-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND The octaheme cytochrome C3 (M(r) 26,000; cc3) from Desulfovibrio desulfuricans Norway is a dimeric cytochrome made up of two identical subunits, each containing four heme groups. It is involved in the redox transfer chain of sulfate-reducing bacteria, which links the periplasmic oxidation of hydrogen to the cytoplasmic reduction of sulfate. The amino-acid sequence of cc3 shows similarities to that of the tetraheme cytochrome c3 (M(r) 13,000; c3) from the same bacteria. Structural analysis of cc3 forms a basis for understanding the precise roles of the multiheme-containing redox proteins and the reason for the presence of several different multiheme cytochromes in one bacterial strain. RESULTS The crystal structure of cytochrome cc3 has been determined at 2.16 A resolution. The subunits display the c3 structural fold with significant amino-acid substitutions, relative to the tetraheme cytochromes c3, in the regions of the dimer interface. The identical subunits are related by a crystallographic twofold axis, with one heme of each subunit in close contact. The overall structure and the environments of the different heme groups are compared with those of the tetraheme cytochromes c3. CONCLUSIONS A common scheme for interactions between these types of cytochrome and their redox partners involves the interaction of a heme crevice, surrounded by positively charged lysine residues, with acidic residues surrounding the redox partner's functional group. Despite the relatively acidic character of cytochrome cc3, the crevice of one heme is surrounded by a high number of positively charged residues, in the same manner as has been reported for cytochromes c3. The environment of this heme is formed by four flexible surface loops which are variable in length and orientation in the different c3-type cytochromes although the overall structural folds are very similar. It has been proposed that this region, adapted in topology and charge, is the interaction site for physiological partners and is also most likely to be the interaction site in the dimeric cytochrome cc3.
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Affiliation(s)
- M Czjzek
- Laboratoire de Cristallographie et Cristallisation des Macromolécules Biologiques, URA 1296, CNRS, Marseille, France
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16
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Lee KB, McLachlan SJ, La Mar GN. Hydrogen isotope effects on the proton nuclear magnetic resonance spectrum of bovine ferricytochrome b5: axial hydrogen bonding involving the axial His-39 imidazole ligand. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1208:22-30. [PMID: 8086435 DOI: 10.1016/0167-4838(94)90155-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The potential role of hydrogen bonding interactions in modulating the molecular and electronic structure of the active site of solubilized bovine ferricytochrome b5 has been investigated by monitoring solvent isotope effects on proton-NMR spectral parameters. It is observed that the hyperfine shifts of both the heme prosthetic group and one coordinated His are sensitive, while those for the other axial His and non-coordinated residues are insensitive, to 2H for 1H exchange. Two types of isotope influences are characterized; one whose chemical shift influence is time-resolved on the NMR time scale, and involves a single proton on one axial ligand, and a second effect which involves multiple protons, is not time resolved, and influences primarily the heme. A large isotope effect on the hyperfine shift is identified for the C beta H signals of His-39 but not His-63. The exchangeable ring NH of His-39 is assigned, and the pH influence on the exchange properties of heme pocket labile protons, when compared to the rate of base catalyzed averaging of the His-39 C beta H isotope effect, lead to the conclusion that the axial hydrogen bond which is responsible for this isotope effect is that between His-39 ring NH and Gly-42 carbonyl. The more rapid exchange of labile protons with solvent for His-63 than His-39 confirms a less solvent accessible and stronger hydrogen bonded His-39 than His-63. The stronger His-39-Gly-42 than His-63-Phe-58 hydrogen bond involving the ring NH leads to more extensive His-39 imidazolate character and hence a stronger iron-His-39 than iron-His-63 bond. The much larger hyperfine shifts for His-39 than His-63 imidazole ring non-labile protons support the stronger bonding of the former ligand, and account for the orientation of the rhombic magnetic axes by His-39 rather than His-63. The solvent isotope effect on the heme leads to rotation of the prosthetic group about the His-Fe-His bond by approximately 0.5 degrees so as to shorten the 7-propionate link to Ser-64. This suggests that the hydrogen bonds between the 7-propionate group and Ser-64 are responsible for the effect.
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Affiliation(s)
- K B Lee
- Department of Chemistry, University of California, Davis 95616
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17
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Armengaud J, Meyer C, Jouanneau Y. Recombinant expression of the fdxD gene of Rhodobacter capsulatus and characterization of its product, a [2Fe-2S] ferredoxin. Biochem J 1994; 300 ( Pt 2):413-8. [PMID: 8002946 PMCID: PMC1138178 DOI: 10.1042/bj3000413] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A gene called fdxD that could potentially code for a ferredoxin has recently been identified upstream of the nitrogenase structural genes in Rhodobacter capsulatus [Willison, Pierrard and Hübner (1993) Gene 133, 39-46]. In the present study, the fdxD gene product has been overproduced in Escherichia coli in a soluble form. The recombinant protein, pink in colour, was purified to homogeneity, and biochemically characterized as a new ferredoxin. It represents the fifth ferredoxin so far identified in R. capsulatus and was designated FdV. Its N-terminal sequence is identical with that of the native ferredoxin isolated from R. capsulatus. U.v-visible-absorption spectra as well as results of c.d. and e.p.r. spectroscopy demonstrated that the fdxD product contained a [2Fe-2S] cluster correctly assembled and incorporated into the polypeptide. Although similar to plant-type ferredoxins, FdV appeared poorly competent in the photo-reduction of NADP+. On the basis of in vitro assays, FdV cannot serve as an electron donor for nitrogenase. The lack of reactivity of FdV in either of these assays may primarily be due to its relatively high mid-point redox potential (E'o = -220 mV, pH 7.5).
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Affiliation(s)
- J Armengaud
- Laboratoire de Biochimie Microbienne (CNRS URA 1130, alliée à l'INSERM), Départment de Biologie Moléculaire et Structurale, Grenoble, France
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18
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Pollock WB, Voordouw G. Molecular biology of c-type cytochromes from Desulfovibrio vulgaris Hildenborough. Biochimie 1994; 76:554-60. [PMID: 7880894 DOI: 10.1016/0300-9084(94)90179-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Sulfate reducing bacteria of the genus Desulfovibrio harbor a wide variety of redox proteins. Three different c-type cytochromes, cytochrome c-553, cytochrome c3 and the high molecular mass cytochrome have been isolated from these bacteria. The high molecular mass cytochrome is part of an operon that encodes a transmembrane protein complex that mediates electron transfer across the cytoplasmic membrane. The physiological function of the other two cytochromes is less clear. They are encoded by monocistronic genes and their redox partners can thus not be identified by gene sequencing. Expression of genes for c-type cytochromes in a foreign host are complicated due to the requirement for covalent heme insertion. Cytochrome c-553 is readily expressed in Escherichia coli in functional form, but cytochrome c3 and the high molecular mass cytochrome are for reasons that are presently not clear.
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Affiliation(s)
- W B Pollock
- Department of Biochemistry, University of British Columbia, Vancouver, Canada
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19
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Czjzek M, Payan F, Haser R. Molecular and structural basis of electron transfer in tetra- and octa-heme cytochromes. Biochimie 1994; 76:546-53. [PMID: 7880893 DOI: 10.1016/0300-9084(94)90178-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The first three-dimensional structure of a dimeric, octa-heme cytochrome c3 (M(r) 26000) from Desulfovibrio desulfuricans Norway, established at 2.2 A resolution, is briefly presented and compared to the known 3-D-structures of different C3-type tetraheme cytochromes, in order to contribute to a better understanding of the function of multiheme clusters and of the role of conserved amino acids implicated in possible electron transfer pathways. The dimeric protein crystallizes in the space group P3(1)21 with a = 73.01 A, c = 61.81 A and the asymmetric unit contains one monomer subunit, the dimer being generated by the crystallographic two-fold axis. The 3-D-structure was solved using the molecular replacement method with a model based on the structure of the tetraheme cytochrome c3 (M(r) 13000) from D desulfuricans Norway, presently refined at 1.7 A resolution. The monomeric subunit has the same overall fold as all cytochromes c3 (M(r) 13000). Moreover, the heme core of all examined cytochromes c3 is highly conserved, but differences appear concerning the heme environments and the histidines, axial ligands of the heme-iron atoms.
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Affiliation(s)
- M Czjzek
- Laboratoire de Cristallographie et Cristallisation des Macromolécules Biologiques, URA 1296, CNRS, Marseille, France
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20
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Garcia D, Richaud P, Breton J, Verméglio A. Structure and function of the tetraheme cytochrome associated to the reaction center of Roseobacter denitrificans. Biochimie 1994; 76:666-73. [PMID: 7893818 DOI: 10.1016/0300-9084(94)90143-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have characterized the tetrahemic RC bound cytochrome isolated from the quasi-photosynthetic bacterium Roseobacter denitrificans in terms of absorption spectrum, redox property and orientation with respect to the membrane plane. The heme, designated H1, which possesses the highest redox midpoint potential (+290 mV), absorbs at 555 nm. Its plane makes an angle of 40 degrees with the membrane plane. The second high potential heme, H2 (+240 mV), peaks at 554 nm and makes a tilt of 55 degrees with the membrane. The two low potential hemes, L1 and L2, present a similar and rather high redox midpoint potential (+90 mV). They absorb at 553 nm and 550 nm. One of these hemes is oriented at 40 degrees while the other makes an angle of 90 degrees with the membrane plane. The soluble cytochrome c551 completes the cyclic electron transfer between the RC and the bc1 complex. Both the oxidation and the re-reduction of cytochrome c551 are diffusible processes. Under semi-aerobic conditions, one of the low potential hemes is photo-oxidized under illumination but only extremely slowly re-reduced. This explains the requirement of high aerobic conditions for growth of Roseobacter denitrificans cells in the light.
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Affiliation(s)
- D Garcia
- CEA, DPVE, SBC, CE de Cadarache, Saint-Paul-lez-Durance, France
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21
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Zannoni D, Daldal F. The role of c-type cytochromes in catalyzing oxidative and photosynthetic electron transport in the dual functional plasmamembrane of facultative phototrophs. Arch Microbiol 1993; 160:413-23. [PMID: 8297207 DOI: 10.1007/bf00245301] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- D Zannoni
- Department of Biology, University of Bologna, Italy
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22
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The ubiquinol:cytochrome c2c oxidoreductase of Chromatium vinosum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90032-b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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23
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Abstract
The quinol oxidase appears to be mainly responsible for the oxidation of the bacterial MKH2 in Bacillus subtilis W23 growing with either glucose or succinate. The activity of the enzyme was maximum with dimethylnaphthoquinol, a water-soluble analogue of the bacterial menaquinol. Menadiol or duroquinol were less actively respired, and naphthoquinol was not oxidized at all. After fourtyfold purification the isolated enzyme contained 5.3 mumol cytochrome aa3 per gram of protein and negligible amounts of cytochrome b and c. The turnover number based on cytochrome aa3 was about 10(3) electrons.s-1 at pH 7 and 37 degrees C. The preparation consisted mainly of a M(r) 57,000 and a M(r) 36,000 polypeptide. The N-terminal amino acid sequence of the latter polypeptide differed from that predicted by the qoxA gene of B. subtilis strain 168 (Santana et al. 1992), in that asp-14 predicted by qoxA was missing in the M(r) 36,000 polypeptide.
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Affiliation(s)
- E Lemma
- Institut für Mikrobiologie, J.-W.-Goethe Universität, Frankfurt am Main, Germany
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24
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von Wachenfeldt C, Hederstedt L. Physico-chemical characterisation of membrane-bound and water-soluble forms of Bacillus subtilis cytochrome c-550. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 212:499-509. [PMID: 8383048 DOI: 10.1111/j.1432-1033.1993.tb17687.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cytochrome c-550 of the Gram-positive bacterium, Bacillus subtilis, is a membrane-bound 13-kDa protein encoded by the cccA gene. The cytochrome has been proposed to be comprised of an N-terminal membrane anchor domain (about 30 residues) which spans the cytoplasmic membrane in an alpha-helical conformation and a C-terminal heme domain (about 70 residues) which is located on the outside of the cytoplasmic membrane. Cytochrome c-550 was purified in the presence of Triton X-100 and characterised. In the reduced state it shows absorption maxima at 415, 521, 550 nm and in the oxidised state a Soret band at 408 nm and a weak band at about 695 nm. The latter absorption band, together with data from amino acid sequence comparisons, strongly suggest His64 and Met99 as the fifth and sixth axial ligands to the heme iron in cytochrome c-550. The midpoint redox potential of the cytochrome, +178 mV, was pH-independent in the pH range 6.0-7.9. Oxidised cytochrome c-550 showed an EPR signal at gmax = 3.41, which is unusual for low-spin cytochromes c with His/Met axial ligation. The heme domain was isolated as a tryptic fragment of 74 residues and as a protein-A-cytochrome-c-550 hybrid protein. Both these forms were water-soluble and showed thermodynamic and spectroscopic properties indistinguishable from the membrane-bound form of cytochrome c-550 and are suitable for structural analysis of the heme domain by X-ray crystallography or NMR techniques. Polypeptide analysis of the membrane-bound and water-soluble tryptic fragment confirmed that B. subtilis cytochrome c-550 in the membrane consists of 120 amino acid residues and has a two-domain structure.
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25
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Howitt CA, Smith GD, Day DA. Cyanide-insensitive oxygen uptake and pyridine nucleotide dehydrogenases in the cyanobacterium Anabaena PCC 7120. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90059-o] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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26
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Brittain T, Blackmore R, Greenwood C, Thomson AJ. Bacterial nitrite-reducing enzymes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:793-802. [PMID: 1425687 DOI: 10.1111/j.1432-1033.1992.tb17350.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The enzymic reduction of nitrite takes place in a wide range of bacteria and is found to occur in denitrifying, assimilatory and dissimilatory pathways. In this review we describe the major molecular characteristics of the various enzymes employed in each of these processes.
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Affiliation(s)
- T Brittain
- Department of Biochemistry, University of Auckland, New Zealand
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27
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Abstract
Haemophilus influenzae is a heme-dependent bacterium. However, little is known of the heme-iron uptake mechanism in this organism. By using a batch ligand affinity chromatography method, a hemin-binding protein of 39,500 molecular weight was isolated from total membranes derived from H. influenzae type b grown under iron-depleted but not under iron-sufficient conditions. Detection of the hemin-binding protein in a whole-cell binding assay demonstrated a surface-exposed location. Competition binding experiments indicated that this hemin-protein interaction was specific, since only hemin or heme-containing proteins, such as human hemoglobin and bovine catalase, but not protoporphyrin IX, iron-loaded human lactoferrin, or transferrin, could abrogate binding. In a limited survey of other H. influenzae strains, an identical hemin-binding protein was isolated, implying that this polypeptide may be structurally and functionally conserved among strains.
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Affiliation(s)
- B C Lee
- Department of Microbiology and Infectious Diseases, University of Calgary, Alberta, Canada
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28
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Matsubara H, Saeki K. Structural and Functional Diversity of Ferredoxins and Related Proteins. ADVANCES IN INORGANIC CHEMISTRY 1992. [DOI: 10.1016/s0898-8838(08)60065-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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29
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Cammack R. Iron—Sulfur Clusters in Enzymes: Themes and Variations. ADVANCES IN INORGANIC CHEMISTRY 1992. [DOI: 10.1016/s0898-8838(08)60066-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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30
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Enzyme localization and orientation of the active site of dissimilatory nitrite reductase from Bacillus firmus. Arch Microbiol 1991. [DOI: 10.1007/bf00418182] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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31
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Arnaud S, Malatesta F, Guigliarelli B, Gayda JP, Bertrand P, Miraglio R, Denis M. Purification and characterization of the oxidase from the marine bacterium Pseudomonas nautica 617. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 198:349-56. [PMID: 1645655 DOI: 10.1111/j.1432-1033.1991.tb16022.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The aerobic respiratory system of the hydrocarbonoclastic marine bacterium Pseudomonas nautica 617 ends with a single terminal oxidase. It is a heme-containing membranous protein which has been demonstrated only to reduce molecular oxygen to hydrogen peroxide [Denis, M., Arnaud S. & Malatesta, F. (1989) FEBS Lett. 247, 475-479]. The purification of this oxidase was achieved in a single step through by DEAE-Trisacryl chromatography. SDS/PAGE showed the presence of four subunits. The pI was found to be 4.45 and a Mr of 130,000 was determined by gel filtration. The amino acid composition of the purified terminal oxidase has been determined. About 52% of the residues are hydrophobic, strengthening the membranous nature of this bacterial oxidase. Room temperature optical spectra are typical of heme b with a 560-nm band for the reduced form in the alpha range. The prosthetic group is made of two hemes b, one high-spin (S = 5/2, gl = 5.9, g parallel approximately 2.0), the other low-spin (S = 1/2, gz = 2.94, gy = 2.27). No other metal centre was detected by EPR. The two hemes remained unresolved in optical spectra, even at low temperature, and throughout redox titration. They behaved potentiometrically like a one-electron, single redox couple, with Em = 87 +/- 10 mV at pH 7.2 and 293 K. The purified oxidase did not oxidize ferrocytochrome c, but displayed quinol oxidase activity both with the native quinone (2419 nmol O2.min-1.mg protein-1 and commercially available coenzyme (101.74 nmol O2.min-1.mg protein-1). Exposure of the reduced enzyme to CO induced the collapse of alpha and beta bands as occurred during reoxidation. In contrast, NaCN and NaN3 fully inhibited the oxidase activity. Results are discussed with respect to other purified quinol oxidases.
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Affiliation(s)
- S Arnaud
- Centre d'Océanologie de Marseille, CNRS URA 41, Parc Scientifique et Technologique de Luminy, Marseille, France
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32
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Abstract
An earlier paper (Wood, P.M. (1983) FEBS Lett. 164, 223-226) proposed that the covalent links that characterize c-type haem originated in order to prevent the haem being lost into the external medium. This is discussed in relation to Gram-negative and Gram-positive bacteria, cyanobacterial thylakoids and eukaryotes. The practical application is for unravelling complex electron transfer chains: c-type cytochromes may be assumed to be absent from the cytoplasm. Sulphate reducing bacteria provide the only confirmed exception to this rule. Examples of non-covalent haem at risk of being lost are considered. Analogies are drawn with flavin and pyrroloquinoline quinone as prosthetic groups.
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Affiliation(s)
- P M Wood
- Department of Biochemistry, University of Bristol, U.K
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33
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Cusanovich MA, Caffrey MS. Biological electron transfer: progress and future directions. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1058:67-70. [PMID: 1646023 DOI: 10.1016/s0005-2728(05)80271-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The rich diversity among bacterial cytochromes has played a key role in the development of our understanding of biological electron transfer. Although studies to date have allowed the elucidation of the contributions of driving force, electrostatics interactions and surface topology to electron transfer kinetics in collision-dependent reactions, much remains to be learned. Little is known about intramolecular and intracomplex electron transfer. Several factors controlling intramolecular and intracomplex electron transfer can be defined. These include driving force, the distance between redox centers, the relative orientation of prosthetic groups, the nature of the intervening media and the molecular dynamics within the electron transfer complex. However, at the present time, we have only a limited understanding of the contribution of these factors to electron transfer kinetics in biologically relevant systems. Nevertheless, a wide range of techniques are now available which should soon provide the information necessary to describe in molecular terms the mechanism of intramolecular and intracomplex electron transfer. Principal among these new approaches are site-directed mutagenesis and NMR spectroscopy.
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Affiliation(s)
- M A Cusanovich
- Department of Biochemistry, University of Arizona, Tucson
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34
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Jones MR, McEwan AG, Jackson JB. The role of c-type cytochromes in the photosynthetic electron transport pathway of Rhodobacter capsulatus. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1019:59-66. [PMID: 2168749 DOI: 10.1016/0005-2728(90)90124-m] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
(1) Short flash excitation of membrane vesicles of a cytochrome-c2-deficient mutant of Rhodobacter capsulatus (strain MT-G4/S4) led to rapid oxidation of a c-type cytochrome. In redox titrations, the photooxidation of c-type cytochrome was attenuated with a midpoint of approx. +360 mV. Vesicles from a control strain, MT1131, gave similar results. These findings are consistent with those of Prince et al. (Prince, R.C., Davidson, E., Haith, L.E. and Daldal, F. (1986) Biochemistry 25, 5208-5214). (2) In anaerobic intact cells the extent of rapid re-reduction of c-type cytochrome oxidised after a flash was less in MT-G/S4 than in MT1131. Cytochrome c reduction in both strains was inhibited by myxothiazol. The myxothiazol-sensitive component of the electrochromic absorbance change in cells indicated that rapid charge separation through the cytochrome bc1 complex was less extensive after a flash in MT-G4/S4 than in MT 1131. (3) In anaerobic intact cells and in chromatophores of Rb. capsulatus strain MT-GS18, a mutant deficient in both cytochrome c1 and cytochrome c2, flash excitation led to the oxidation of c-type cytochrome. Redox titrations and spectra of chromatophores suggested that this is the same cytochrome as was photooxidized in vesicles of MT-G4/S4 and MT1131. This result is in contrast with earlier findings (Prince, R.C. and Daldal, F. (1987) Biochim. Biophys, Acta 894, 370-378) in which it was reported that no photooxidation of c-type cytochrome occurred in the absence of c1 and c2, and argues against the possibility that cytochrome c1 can rapidly and directly donate electrons to the reaction centre. (4) It is proposed that a previously uncharacterized, membrane-bound c-type cytochrome (Em7 approximately +360 mV) is present in Rb-capsulatus MT1131, in the c2-deficient mutant MT-G4/34 and in the c1/c2-deficient mutant MTGS18. This cytochrome and cytochrome c2 are alternative electron donors to the reaction centre in strain MT1131.
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Affiliation(s)
- M R Jones
- School of Biochemistry, University of Birmingham, U.K
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