PDBsum entry 1fp4

Oxidoreductase

PDB id: 1fp4

Contents

Protein chains

467 a.a. *

522 a.a. *

Ligands

HCA ×2

CFM ×2

CLP ×2

Metals

_CA ×2

Waters ×433

* Residue conservation analysis

PDB id:

1fp4

Name:

Oxidoreductase

Title:

Crystal structure of the alpha-h195q mutant of nitrogenase

Structure:

Nitrogenase molybdenum-iron protein alpha chain. Chain: a, c. Engineered: yes. Mutation: yes. Nitrogenase molybdenum-iron protein beta chain. Chain: b, d. Engineered: yes

Source:

Azotobacter vinelandii. Organism_taxid: 354. Organism_taxid: 354

Biol. unit:

Tetramer (from PQS)

Resolution:

2.50Å R-factor: 0.184 R-free: 0.240

Authors:

M.Sorlie,J.Christiansen,B.J.Lemon,J.W.Peters,D.R.Dean,B.J.Hales

Key ref:

M.Sørlie et al. (2001). Mechanistic features and structure of the nitrogenase alpha-Gln195 MoFe protein. Biochemistry, 40, 1540-1549. PubMed id: 11327812 DOI: 10.1021/bi0013997

Date:

30-Aug-00 Release date: 20-Nov-02

Protein chains

P07328  (NIFD_AZOVI) -  Nitrogenase molybdenum-iron protein alpha chain from Azotobacter vinelandii

Seq: 492 a.a.

Struc: 467 a.a.*

Protein chains

P07329  (NIFK_AZOVI) -  Nitrogenase molybdenum-iron protein beta chain from Azotobacter vinelandii

Seq: 523 a.a.

Struc: 522 a.a.

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: Chains A, B, C, D: E.C.1.18.6.1 - nitrogenase.
• Pathway: Nitrogenase
• Reaction: N2 + 8 reduced [2Fe-2S]-[ferredoxin] + 16 ATP + 16 H2O = H2 + 8 oxidized [2Fe-2S]-[ferredoxin] + 2 NH4⁺ + 16 ADP + 16 phosphate + 6 H⁺
• Cofactor: Iron-sulfur; Vanadium cation or Mo cation

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi0013997

Biochemistry 40:1540-1549 (2001)

PubMed id: 11327812

Mechanistic features and structure of the nitrogenase alpha-Gln195 MoFe protein.

M.Sørlie, J.Christiansen, B.J.Lemon, J.W.Peters, D.R.Dean, B.J.Hales.

ABSTRACT

EPR signals observed under CO and C(2)H(2) during nitrogenase turnover were investigated for the alpha-Gln(195) MoFe protein, an altered form for which the alpha-His(195) residue has been substituted by glutamine. Under CO, samples show S = 1/2 hi- and lo-CO EPR signals identical to those recognized for the wild-type protein, whereas the S = 3/2 signals generated under high CO/high flux conditions differ. Previous work has revealed that the EPR spectrum generated under C(2)H(2) exhibits a signal (S(EPR1)) originating from the FeMo-cofactor having two or more bound C(2)H(2) adducts and a second signal (S(EPR2)) arising from a radical species [Sørlie, M., Christiansen, J., Dean, D. R., and Hales, B. J. (1999) J. Am. Chem. Soc. 121, 9457-9458]. Pressure-dependent studies show that the intensity of these signals has a sigmoidal dependency at low pressures and maximized at 0.1 atm C(2)H(2) with a subsequent decrease in steady-state intensity at higher pressures. Analogous signals are not recognized for the wild-type MoFe protein. Analysis of the principal g-factors of S(EPR2) suggests that it either represents an unusual metal cluster or is a carboxylate centered radical possibly originating from homocitrate. Both S(EPR1) and S(EPR2) exhibit similar relaxation properties that are atypical for S = 1/2 signals originating from Fe-S clusters or radicals and indicate a coupled relaxation pathway. The alpha-Gln(195) MoFe protein also exhibits these signals when incubated under turnover conditions in the presence of C(2)H(4). Under these conditions, additional inflections in the g 4-6 region assigned to ground-state transitions of an S = 3/2 spin system are also recognized and assigned to turnover states of the MoFe protein without C(2)H(4) bound. The structure of alpha-Gln(195) was crystallographically determined and found to be virtually identical to that of the wild-type MoFe protein except for replacement of an NuH-S hydrogen bond interaction between FeMo-cofactor and the imidazole side chain of alpha-His(195) by an analogous interaction involving Gln.