The Characterization of Different Flavodoxin Reductase-Flavodoxin (FNR-Fld) Interactions Reveals an Efficient FNR-Fld Redox Pair and Identifies a Novel FNR Subclass
Flavodoxins (Flds) are small, bacterial proteins that transfer electrons to various redox enzymes. Flavodoxins are reduced by ferredoxin/flavodoxin NADP+ oxidoreductases (FNRs), but little is known of the FNR-Fld interaction. Here, we compare the interactions of two flavodoxins (Fld1-2), one flavodoxin-like protein (NrdI), and three different thioredoxin reductase (TrxR)-like FNRs (FNR1-3), all from Bacillus cereus. Steady-state kinetics shows that the FNR2-Fld2 electron transfer pair is particularly efficient, and redox potential measurements also indicate that this is the most favorable electron donor/acceptor pair. Furthermore, crystal structures of FNR1 and FNR2 show that the proteins have crystallized in different conformations, a closed and an open conformation, respectively. We suggest that a large-scale conformational rearrangement takes place during the FNR catalytic cycle to allow for the binding and reduction of the Fld and, subsequently, the re-reduction of the FNR by NADPH. Finally, inspection of the residues surrounding the FAD cofactor in the FNR active site shows that a key isoalloxazine ring-stacking residue is different in FNR1 and FNR2, which could explain the large difference in catalytic efficiency between the two FNRs. To date, all of the characterized TrxR-like FNRs have a residue with aromatic character stacking against the FAD isoalloxazine ring, and this has been thought to be a conserved feature of this class of FNRs. FNR1, however, has a valine in this position. Bioinformatic analysis shows that the TrxR-like FNRs can actually be divided into two groups, one group where the FAD-stacking residue has aromatic character and another group where it is valine.
| Medienart: |
E-Artikel |
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| Erscheinungsjahr: |
2018 |
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| Erschienen: |
2018 |
| Enthalten in: |
Zur Gesamtaufnahme - volume:57 |
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| Enthalten in: |
Biochemistry - 57(2018), 37 vom: 18. Sept., Seite 5427-5436 |
| Sprache: |
Englisch |
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| Beteiligte Personen: |
Gudim, Ingvild [VerfasserIn] |
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| Links: |
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| Themen: |
EC 1.6.- |
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| Anmerkungen: |
Date Completed 05.07.2019 Date Revised 05.07.2019 published: Print-Electronic Citation Status MEDLINE |
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| doi: |
10.1021/acs.biochem.8b00674 |
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| funding: |
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| Förderinstitution / Projekttitel: |
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| PPN (Katalog-ID): |
NLM287804208 |
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| 100 | 1 | |a Gudim, Ingvild |e verfasserin |4 aut | |
| 245 | 1 | 4 | |a The Characterization of Different Flavodoxin Reductase-Flavodoxin (FNR-Fld) Interactions Reveals an Efficient FNR-Fld Redox Pair and Identifies a Novel FNR Subclass |
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| 500 | |a Date Completed 05.07.2019 | ||
| 500 | |a Date Revised 05.07.2019 | ||
| 500 | |a published: Print-Electronic | ||
| 500 | |a Citation Status MEDLINE | ||
| 520 | |a Flavodoxins (Flds) are small, bacterial proteins that transfer electrons to various redox enzymes. Flavodoxins are reduced by ferredoxin/flavodoxin NADP+ oxidoreductases (FNRs), but little is known of the FNR-Fld interaction. Here, we compare the interactions of two flavodoxins (Fld1-2), one flavodoxin-like protein (NrdI), and three different thioredoxin reductase (TrxR)-like FNRs (FNR1-3), all from Bacillus cereus. Steady-state kinetics shows that the FNR2-Fld2 electron transfer pair is particularly efficient, and redox potential measurements also indicate that this is the most favorable electron donor/acceptor pair. Furthermore, crystal structures of FNR1 and FNR2 show that the proteins have crystallized in different conformations, a closed and an open conformation, respectively. We suggest that a large-scale conformational rearrangement takes place during the FNR catalytic cycle to allow for the binding and reduction of the Fld and, subsequently, the re-reduction of the FNR by NADPH. Finally, inspection of the residues surrounding the FAD cofactor in the FNR active site shows that a key isoalloxazine ring-stacking residue is different in FNR1 and FNR2, which could explain the large difference in catalytic efficiency between the two FNRs. To date, all of the characterized TrxR-like FNRs have a residue with aromatic character stacking against the FAD isoalloxazine ring, and this has been thought to be a conserved feature of this class of FNRs. FNR1, however, has a valine in this position. Bioinformatic analysis shows that the TrxR-like FNRs can actually be divided into two groups, one group where the FAD-stacking residue has aromatic character and another group where it is valine | ||
| 650 | 4 | |a Journal Article | |
| 650 | 4 | |a Research Support, Non-U.S. Gov't | |
| 650 | 7 | |a Flavodoxin |2 NLM | |
| 650 | 7 | |a NADH, NADPH Oxidoreductases |2 NLM | |
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| 650 | 7 | |a flavodoxin NADPH oxidoreductase |2 NLM | |
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| 700 | 1 | |a Hammerstad, Marta |e verfasserin |4 aut | |
| 700 | 1 | |a Lofstad, Marie |e verfasserin |4 aut | |
| 700 | 1 | |a Hersleth, Hans-Petter |e verfasserin |4 aut | |
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| 856 | 4 | 0 | |u http://dx.doi.org/10.1021/acs.biochem.8b00674 |3 Volltext |
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