S
IPR030655

NifH/chlL conserved site

InterPro entry
Short nameNifH/chlL_CS

Description

Nitrogenase (
1.18.6.1
)
[2]
is the enzyme system responsible for biological nitrogen fixation. Nitrogenase is an oligomeric complex which consists of two components: component 1 which contains the active site for the reduction of nitrogen to ammonia and component 2 (also called the iron protein).

Component 2 is a homodimer of a protein (gene nifH) which binds a single 4Fe-4S iron sulfur cluster
[3]
. In the nitrogen fixation process nifH is first reduced by a protein such as ferredoxin; the reduced protein then transfers electrons to component 1 with the concomitant consumption of ATP.

A number of proteins are known to be evolutionary related to nifH. These proteins are:


 * Chloroplast encoded chlL (or frxC) protein
[1]
. ChlL is encoded on the chloroplast genome of some plant species, its exact function is not known, but it could act as an electron carrier in the conversion of protochlorophyllide to chlorophyllide.
 * Photosynthetic bacteria proteins bchL and bchX
[4]
. These proteins are also likely to play a role in chlorophyll synthesis.


There are a number of conserved regions in the sequence of these proteins: in the N-terminal section there is an ATP-binding site motif 'A' (P-loop) and in the central section there are two conserved cysteines which have been shown, in nifH, to be the ligands of the 4Fe-4S cluster. This entry represents two conserved sites which correspond to the regions around these cysteines.

References

1.Identification of a novel nifH-like (frxC) protein in chloroplasts of the liverwort Marchantia polymorpha. Fujita Y, Takahashi Y, Kohchi T, Ozeki H, Ohyama K, Matsubara H. Plant Mol. Biol. 13, 551-61, (1989). View articlePMID: 2491672

2.Nitrogenases without molybdenum. Pau RN. Trends Biochem. Sci. 14, 183-6, (1989). View articlePMID: 2672439

3.Crystallographic structure of the nitrogenase iron protein from Azotobacter vinelandii. Georgiadis MM, Komiya H, Chakrabarti P, Woo D, Kornuc JJ, Rees DC. Science 257, 1653-9, (1992). View articlePMID: 1529353

4.The Rhodobacter capsulatus chlorin reductase-encoding locus, bchA, consists of three genes, bchX, bchY, and bchZ. Burke DH, Alberti M, Hearst JE. J. Bacteriol. 175, 2407-13, (1993). View articlePMID: 8468299

Cross References

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