Conserved Site

NifH/chlL conserved site (IPR030655)

Short name: NifH/chlL_CS


Nitrogenase (EC: [PMID: 2672439] 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 [PMID: 1529353]. 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 [PMID: 2491672]. 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 [PMID: 8468299]. 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.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns
PROSITE patterns