Ferredoxin-NADP+ reductase (adrenodoxin-type)

 

Bovine adrenodoxin (Adx) is a ferredoxin involved in the electron transfer from the flavoenzyme NADPH-adrenodoxin-reductase (AdR) to two P450 cytochromes; this process occurs in the production of steroid hormones.

 

Reference Protein and Structure

Sequence
P08165 UniProt (1.18.1.6) IPR021163 (Sequence Homologues) (PDB Homologues)
Biological species
Bos taurus (Cattle) Uniprot
PDB
1e6e - ADRENODOXIN REDUCTASE/ADRENODOXIN COMPLEX OF MITOCHONDRIAL P450 SYSTEMS (2.3 Å) PDBe PDBsum 1e6e
Catalytic CATH Domains
3.50.50.60 CATHdb 3.40.50.720 CATHdb (see all for 1e6e)
Cofactors
Fadh2(2-) (1)
Click To Show Structure

Enzyme Reaction (EC:1.18.1.2)

di-mu-sulfido-diiron(2+)
CHEBI:33737ChEBI
+
NADPH(4-)
CHEBI:57783ChEBI
→
di-mu-sulfido-diiron(1+)
CHEBI:33738ChEBI
+
NADP(3-)
CHEBI:58349ChEBI
+
hydron
CHEBI:15378ChEBI
Alternative enzyme names: NADP(+):ferredoxin oxidoreductase, NADPH:ferredoxin oxidoreductase, TPNH-ferredoxin reductase, Ferredoxin-NADP(+) oxidoreductase, Ferredoxin-NADP(+) reductase, Ferredoxin-TPN reductase, Ferredoxin-nicotinamide adenine dinucleotide phosphate reductase, Ferredoxin-nicotinamide-adenine dinucleotide phosphate (oxidized) reductase,

Enzyme Mechanism

Introduction

AdR has a bound FAD cofactor. NADPH docks and transfers its hydride to FAD. An electron from FADH- is transferred, via the main chain atoms of Ile 376 and then Thr 377, to the bound half of an Adx dimer (to its Cys 52, then to the [2Fe-2S] centre). The electron is then transferred to the non-AdR-bound Adx molecule which dissociates. The second electron from FADH. is transferred the remaining Adx by the same route; this is concomitant with proton transfer from FADH. to a water molecule bound, and made more basic, by Asp 159 and His 55.

Catalytic Residues Roles

UniProt PDB* (1e6e)
His87 His55A His 55 binds water and makes it more basic. hydrogen bond acceptor, electrostatic stabiliser
Asp191 Asp159A Asp 159 binds water and makes it more basic. hydrogen bond acceptor, electrostatic stabiliser
Ile408 (main-N) Ile376A (main-N) The main chain of Ile 276 is part of an electron transfer chain from FADH- and FADH. to adrenodoxin. single electron relay, single electron acceptor, single electron donor, polar interaction
Thr409 (main-C) Thr377A (main-C) The main chain of Thr 377 is part of an electron transfer chain from FADH- and FADH. to adrenodoxin. single electron relay, single electron acceptor, single electron donor, polar interaction
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

aromatic unimolecular elimination by the conjugate base, hydride transfer, aromatic bimolecular nucleophilic addition, overall reactant used, cofactor used, intermediate formation, overall product formed, redox reaction, radical formation, electron relay, proton transfer, electron transfer, radical termination, intermediate terminated, native state of cofactor regenerated, native state of enzyme regenerated

References

  1. Ziegler GA et al. (2000), Biochemistry, 39, 10986-10995. Crystal Structures of Adrenodoxin Reductase in Complex with NADP+and NADPH Suggesting a Mechanism for the Electron Transfer of an Enzyme Family†,‡. DOI:10.1021/bi000079k. PMID:10998235.
  2. Beilke D et al. (2002), Biochemistry, 41, 7969-7978. A New Electron Transport Mechanism in Mitochondrial Steroid Hydroxylase Systems Based on Structural Changes upon the Reduction of Adrenodoxin†. DOI:10.1021/bi0160361. PMID:12069587.
  3. Müller JJ et al. (2001), J Biol Chem, 276, 2786-2789. Adrenodoxin Reductase-Adrenodoxin Complex Structure Suggests Electron Transfer Path in Steroid Biosynthesis. DOI:10.1074/jbc.m008501200. PMID:11053423.

Step 1. A hydride ion is transferred from the substrate NADP to the cofactor, FAD461.

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Catalytic Residues Roles

Residue Roles
His55A hydrogen bond acceptor
Asp159A hydrogen bond acceptor
Ile376A (main-N) polar interaction
Thr377A (main-C) polar interaction

Chemical Components

ingold: aromatic unimolecular elimination by the conjugate base, hydride transfer, ingold: aromatic bimolecular nucleophilic addition, overall reactant used, cofactor used, intermediate formation, overall product formed

Step 2. A single electron is transferred from the FAD461 to one of the substrate adrenodoxin dmers via the main chains of Ile376 and Thr377 and a second adrenodoxin dimer.

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Catalytic Residues Roles

Residue Roles
His55A hydrogen bond acceptor
Asp159A hydrogen bond acceptor
Ile376A (main-N) polar interaction
Thr377A (main-C) polar interaction
Ile376A (main-N) single electron relay
Thr377A (main-C) single electron relay, single electron acceptor, single electron donor
Ile376A (main-N) single electron acceptor, single electron donor

Chemical Components

redox reaction, radical formation, overall reactant used, intermediate formation, overall product formed, electron relay

Step 3. FAD461 is deprotonated by a water molecule activated by Asp159. This results in the second electron transfer from FAD461 to the second adrenodoxin dimer via the main chains of Ile376 and Thr377.

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Catalytic Residues Roles

Residue Roles
His55A hydrogen bond acceptor, electrostatic stabiliser
Asp159A hydrogen bond acceptor, electrostatic stabiliser
Ile376A (main-N) polar interaction
Thr377A (main-C) polar interaction
Ile376A (main-N) single electron donor
Thr377A (main-C) single electron acceptor
Ile376A (main-N) single electron relay
Thr377A (main-C) single electron relay
Ile376A (main-N) single electron acceptor
Thr377A (main-C) single electron donor

Chemical Components

proton transfer, electron transfer, radical termination, intermediate terminated, overall product formed, electron relay, native state of cofactor regenerated, native state of enzyme regenerated
Download: Image, Marvin File

Step 1. A hydride ion is transferred from the substrate NADP to the cofactor, FAD461.

Step 2. A single electron is transferred from the FAD461 to one of the substrate adrenodoxin dmers via the main chains of Ile376 and Thr377 and a second adrenodoxin dimer.

Step 3. FAD461 is deprotonated by a water molecule activated by Asp159. This results in the second electron transfer from FAD461 to the second adrenodoxin dimer via the main chains of Ile376 and Thr377.

Products.

Contributors

Gemma L. Holliday, Daniel E. Almonacid, Jonathan T. W. Ng