1QH8: NITROGENASE MOFE PROTEIN FROM KLEBSIELLA PNEUMONIAE, AS-CRYSTALLIZED (MIXED OXIDATION) STATE

Citation:
Abstract
The X-ray crystal structure of Klebsiella pneumoniae nitrogenase component 1 (Kp1) has been determined and refined to a resolution of 1.6 A, the highest resolution reported for any nitrogenase structure. Models derived from three 1.6 A resolution X-ray data sets are described; two represent distinct oxidation states, whilst the third appears to be a mixture of both oxidized and reduced states (or perhaps an intermediate state). The structures of the protein and the iron-molybdenum cofactor (FeMoco) appear to be largely unaffected by the redox status, although the movement of Ser beta90 and a surface helix in the beta subunit may be of functional significance. By contrast, the 8Fe-7S P-cluster undergoes discrete conformational changes involving the movement of two iron atoms. Comparisons with known component 1 structures reveal subtle differences in the FeMoco environment, which could account for the lower midpoint potential of this cluster in Kp1. Furthermore, a non-proline- cis peptide bond has been identified in the alpha subunit that may have a functional role. It is within 10 A of the FeMoco and may have been overlooked in other component 1 models. Finally, metal-metal and metal-sulphur distances within the metal clusters agree well with values derived from EXAFS studies, although they are generally longer than the values reported for the closely related protein from Azotobacter vinelandii. A number of bonds between the clusters and their ligands are distinctly longer than the EXAFS values, in particular, those involving the molybdenum atom of the FeMoco.
PDB ID: 1QH8Download
MMDB ID: 11294
PDB Deposition Date: 1999/5/11
Updated in MMDB: 1999/11
Experimental Method:
x-ray diffraction
Resolution: 1.6  Å
Source Organism:
Similar Structures:
Biological Unit for 1QH8: tetrameric; determined by author and by software (PISA)
Molecular Components in 1QH8
Label Count Molecule
Proteins (4 molecules)
2
Protein (Nitrogenase Molybdenum Iron Protein)
Molecule annotation
2
Protein (Nitrogenase Molybdenum Iron Protein)
Molecule annotation
Chemicals (32 molecules)
1
7
2
2
3
2
4
2
5
17
6
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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