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Utschig LM, Brahmachari U, Mulfort KL, Niklas J, Poluektov OG. Biohybrid photosynthetic charge accumulation detected by flavin semiquinone formation in ferredoxin-NADP + reductase. Chem Sci 2022; 13:6502-6511. [PMID: 35756516 PMCID: PMC9172293 DOI: 10.1039/d2sc01546c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Flavin chemistry is ubiquitous in biological systems with flavoproteins engaged in important redox reactions. In photosynthesis, flavin cofactors are used as electron donors/acceptors to facilitate charge transfer and accumulation for ultimate use in carbon fixation. Following light-induced charge separation in the photosynthetic transmembrane reaction center photosystem I (PSI), an electron is transferred to one of two small soluble shuttle proteins, a ferredoxin (Fd) or a flavodoxin (Fld) (the latter in the condition of Fe-deficiency), followed by electron transfer to the ferredoxin-NADP+ reductase (FNR) enzyme. FNR accepts two of these sequential one electron transfers, with its flavin adenine dinucleotide (FAD) cofactor becoming doubly reduced, forming a hydride which is then passed onto the substrate NADP+ to form NADPH. The two one-electron potentials (oxidized/semiquinone and semiquinone/hydroquinone) are similar to each other with the FNR protein stabilizing the hydroquinone, making spectroscopic detection of the intermediate semiquinone state difficult. We employed a new biohybrid-based strategy that involved truncating the native three-protein electron transfer cascade PSI → Fd → FNR to a two-protein cascade by replacing PSI with a molecular Ru(ii) photosensitizer (RuPS) which is covalently bound to Fd and Fld to form biohybrid complexes that successfully mimic PSI in light-driven NADPH formation. RuFd → FNR and RuFld → FNR electron transfer experiments revealed a notable distinction in photosynthetic charge accumulation that we attribute to the different protein cofactors [2Fe2S] and flavin. After freeze quenching the two-protein systems under illumination, an intermediate semiquinone state of FNR was readily observed with cw X-band EPR spectroscopy. The increased spectral resolution from selective deuteration allowed EPR detection of inter-flavoprotein electron transfer. This work establishes a biohybrid experimental approach for further studies of photosynthetic light-driven electron transfer chain that culminates at FNR and highlights nature's mechanisms that couple single electron transfer chemistry to charge accumulation, providing important insight for the development of photon-to-fuel schemes.
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Affiliation(s)
- Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Udita Brahmachari
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Karen L Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
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Soltau SR, Dahlberg PD, Niklas J, Poluektov OG, Mulfort KL, Utschig LM. Ru-protein-Co biohybrids designed for solar hydrogen production: understanding electron transfer pathways related to photocatalytic function. Chem Sci 2016; 7:7068-7078. [PMID: 28451142 PMCID: PMC5355951 DOI: 10.1039/c6sc03121h] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 08/05/2016] [Indexed: 12/12/2022] Open
Abstract
Two ruthenium-protein-cobaloxime biohybrids produce photocatalytic hydrogen through different catalytic pathways characterized by EPR and transient optical spectroscopies.
A series of Ru–protein–Co biohybrids have been prepared using the electron transfer proteins ferredoxin (Fd) and flavodoxin (Fld) as scaffolds for photocatalytic hydrogen production. The light-generated charge separation within these hybrids has been monitored by transient optical and electron paramagnetic resonance spectroscopies. Two distinct electron transfer pathways are observed. The Ru–Fd–Co biohybrid produces up to 650 turnovers of H2 utilizing an oxidative quenching mechanism for Ru(ii)* and a sequential electron transfer pathway via the native [2Fe–2S] cluster to generate a Ru(iii)–Fd–Co(i) charge separated state that lasts for ∼6 ms. In contrast, a direct electron transfer pathway occurs for the Ru–ApoFld–Co biohybrid, which lacks an internal electron relay, generating Ru(i)–ApoFld–Co(i) charge separated state that persists for ∼800 μs and produces 85 turnovers of H2 by a reductive quenching mechanism for Ru(ii)*. This work demonstrates the utility of protein architectures for linking donor and catalytic function via direct or sequential electron transfer pathways to enable stabilized charge separation which facilitates photocatalysis for solar fuel production.
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Affiliation(s)
- Sarah R Soltau
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544
| | - Peter D Dahlberg
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544.,Graduate Program in Biophysics , The University of Chicago , Chicago , IL 60637 , USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544
| | - Karen L Mulfort
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544
| | - Lisa M Utschig
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , IL 60439 , USA . ; Tel: +1-630-252-3544
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Geider RJ, La Roche J. The role of iron in phytoplankton photosynthesis, and the potential for iron-limitation of primary productivity in the sea. PHOTOSYNTHESIS RESEARCH 1994; 39:275-301. [PMID: 24311126 DOI: 10.1007/bf00014588] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/1993] [Accepted: 09/29/1993] [Indexed: 05/12/2023]
Abstract
Iron supply has been suggested to influence phytoplankton biomass, growth rate and species composition, as well as primary productivity in both high and low NO3 (-) surface waters. Recent investigations in the equatorial Pacific suggest that no single factor regulates primary productivity. Rather, an interplay of bottom-up (i.e., ecophysiological) and top-down (i.e., ecological) factors appear to control species composition and growth rates. One goal of biological oceanography is to isolate the effects of single factors from this multiplicity of interactions, and to identify the factors with a disproportionate impact. Unfortunately, our tools, with several notable exceptions, have been largely inadequate to the task. In particular, the standard technique of nutrient addition bioassays cannot be undertaken without introducing artifacts. These so-called 'bottle effects' include reducing turbulence, isolating the enclosed sample from nutrient resupply and grazing, trapping the isolated sample at a fixed position within the water column and thus removing it from vertical movement through a light gradient, and exposing the sample to potentially stimulatory or inhibitory substances on the enclosure walls. The problem faced by all users of enrichment experiments is to separate the effects of controlled nutrient additions from uncontrolled changes in other environmental and ecological factors. To overcome these limitations, oceanographers have sought physiological or molecular indices to diagnose nutrient limitation in natural samples. These indices are often based on reductions in the abundance of photosynthetic and other catalysts, or on changes in the efficiency of these catalysts. Reductions in photosynthetic efficiency often accompany nutrient limitation either because of accumulation of damage, or impairment of the ability to synthesize fully functional macromolecular assemblages. Many catalysts involved in electron transfer and reductive biosyntheses contain iron, and the abundances of most of these catalysts decline under iron-limited conditions. Reductions of ferredoxin or cytochrome f content, nitrate assimilation rates, and dinitrogen fixation rates are amongst the diagnostics that have been used to infer iron limitation in some marine systems. An alternative approach to diagnosing iron-limitation uses molecules whose abundance increases in response to iron-limitation. These include cell surface iron-transport proteins, and the electron transfer protein flavodoxin which replaces the Fe-S protein ferredoxin in many Fe-deficient algae and cyanobacteria.
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Affiliation(s)
- R J Geider
- College of Marine Studies, University of Delaware, 19958-1298, Lewes, DE, USA
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Yakunin AF, Hallenbeck PC, Gogotov IN. Purification and properties of a flavodoxin from the heterocystous cyanobacterium Anabaena sphaerica. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1164:305-10. [PMID: 8343530 DOI: 10.1016/0167-4838(93)90263-q] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A flavodoxin was purified to homogeneity from the nitrogen-fixing heterocystous cyanobacterium Anabaena sphaerica grown under iron-limited conditions. The protein has a molecular mass of 21 kDa, and its spectral properties and amino-acid composition are very close to that of flavodoxins from other cyanobacteria. A. sphaerica flavodoxin supported the activities of A. sphaerica NADP reductase and Clostridium butyricum hydrogenase in reconstituted systems with illuminated plant chloroplasts as reductant. With the use of polyclonal anti-flavodoxin antiserum it was found that nitrogen-fixing cultures of A. sphaerica grown under iron-sufficient conditions contain low but significant amounts of flavodoxin (0.2-0.6 micrograms/mg crude extract protein) which increased dramatically (to 8-15 micrograms/mg crude extract protein) after the iron concentration in the medium was decreased to below 1 microM Fe. The flavodoxin content of both iron-limited and iron-sufficient. A. sphaerica was also shown to depend upon the growth phase of the (batch) cultures with a maximum at early exponential phase, coinciding with maximal in-vivo nitrogenase activity. These results suggest that A. sphaerica flavodoxin not only substitutes for ferredoxin under iron-limiting conditions, but also fulfills some specific role under iron-sufficient conditions.
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Affiliation(s)
- A F Yakunin
- Institute of Soil Science and Photosynthesis, Pushchino, Moscow region, Russia
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Abstract
The redox potentials of flavodoxins from the cyanobacteria Synechococcus PCC 6301 (formerly Anacystis nidulans) and Nostoc strain MAC, and from the red alga Chondrus crispus, were determined by potentiometric titration. For the oxidized-semiquinone interconversion the potentials at pH 7.0 of the three flavodoxins were between -210 and -235 mV, and these were pH-dependent over the range pH 6.9-8.2. For the semiquinone-reduced interconversion the potentials of the cyanobacterial flavodoxins were close to -414 mV, and that for the algal flavodoxin, -370 mV, is the highest reported in this group of flavoproteins.
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Tollin G, Edmondson DE. [37] Purification and properties of flavodoxins. Methods Enzymol 1980. [DOI: 10.1016/s0076-6879(80)69039-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
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Klein ER, Klein PD. A selected bibliography of biomedical and environmental applications of stable isotopes. I--Deuterium 1971-1976. BIOMEDICAL MASS SPECTROMETRY 1978; 5:91-111. [PMID: 343824 DOI: 10.1002/bms.1200050202] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A compilation of selected references to the use of deuterium in biochemical, pharmacological, clinical and environmental applications for the period 1971-1976 is presented. As a further aid, author and subject indices have been compiled.
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Hutber G, Hutson K, Rogers L. Effect of iron dificiency on levels of two ferredoxins and flavodoxin in a cyanobacterium. FEMS Microbiol Lett 1977. [DOI: 10.1111/j.1574-6968.1977.tb00612.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Yamamoto T, Palmer G, Crespi H. Resonance raman studies of a c type algal cytochrome. Deuterium shifts and a comparison with mammalian cytochrome c. BIOCHIMICA ET BIOPHYSICA ACTA 1976; 439:232-9. [PMID: 182237 DOI: 10.1016/0005-2795(76)90178-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A c type cytochrome isolated from Synechococcus lividus grown on water and 2H2O media, has been studied by resonance Raman spectroscopy. The spectra were taken on the oxidized and reduced protein with excitation within the Soret band at 441.6 nm to determine whether individual resonance Raman bands of the heme shift upon deuterium substitution and also to provide a comparison with the spectra of horse heart cytochrome c. Some of the shifts observed with the deuterated heme c are larger than the corresponding shifts in meso-deuterated metalloporphyrins suggesting mixing of peripheral substituent vibrations with the skeletal modes of the porphyrin macrocycle. The algal cytochrome exhibits resonance Raman spectra roughly similar to those of horse heart cytochrome c, consistent with its optical absorption spectra which is typical of c type cytochromes, although a detailed comparison reveals note-worthy differences between the spectra of the two proteins; this may be a reflection of the effect of non-methionine ligands and protein environment on the vibrations of the c type heme in the algal cytochrome.
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Kirschenbaum DM. A compilation of amino acid analyses of proteins. VII. Residues per molecule-5. Anal Biochem 1975; 66:123-50. [PMID: 1096669 DOI: 10.1016/0003-2697(75)90732-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Crespi HL, Kostka AG, Smith UH. Proton Magnetic resonance observations of hydrogen exchange rates and secondary structure in algal ferredoxin. Biochem Biophys Res Commun 1974; 61:1407-14. [PMID: 4218105 DOI: 10.1016/s0006-291x(74)80440-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Kirschenbaum DM. A compilation of amino acid analyses of proteins VI residues per molecule. IV. Anal Biochem 1974; 61:567-609. [PMID: 4608596 DOI: 10.1016/0003-2697(74)90425-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Tanaka M, Haniu M, Yasunobu KT, Mayhew S, Massey V. The Primary Structure of Peptostreptococcus elsdenii Flavodoxin. J Biol Chem 1973. [DOI: 10.1016/s0021-9258(19)43779-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Norris JR, Crespi HL, Katz JJ. Characterization of a new photo-ESR signal associated with photosynthesis. Biochem Biophys Res Commun 1972; 49:139-46. [PMID: 4342720 DOI: 10.1016/0006-291x(72)90020-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Norris J, Crespi H. Analysis of in vivo and in vitro ESR spectra of 2H-flavin, an intrinsic spin label of flavoproteins. Chem Phys Lett 1972. [DOI: 10.1016/0009-2614(72)80420-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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