{PDOC00085} {PS00699; NITROGENASE_1_1} {PS00090; NITROGENASE_1_2} {BEGIN} *************************************************************** * Nitrogenases component 1 alpha and beta subunits signatures * *************************************************************** Nitrogenase (EC 1.18.6.1) [1] is the enzyme system responsible for biological nitrogen fixation. Nitrogenase is an oligomeric complex which consists of two components: component 2 is an homodimer of an iron-sulfur protein, while component 1 which contains the active site for the reduction of nitrogen to ammonia exists in three different forms: - A molybdenum-iron containing protein (MoFe). The MoFe protein is a hetero- tetramer consisting of two pairs of alpha (nifD) and beta (nifK) subunits. - A vanadium-iron containing protein (VFe). The VFe protein is a hexamer of two pairs each of alpha (vnfD), beta (vnfK), and delta (vnfG) subunits. - The third form of component 1 seems to only contain iron. Like the vanadium form it is a hexamer composed of alpha (anfD), beta (anfK), and delta (anfG) subunits. The alpha and beta chains of the three types of component 1 are evolutionary related and they are also related to proteins nifE and nifN, which are most probably involved in the iron-molybdenum cofactor biosynthesis [2]. We selected as signature patterns for this family of proteins two stretches of residues which are located in the N-terminal section and which each contain a conserved cysteine thought to be one of the ligands for the metal-sulfur clusters. -Consensus pattern: [LIVMFYH]-[LIVMFST]-H-[AG]-[AGSP]-[LIVMNQA]-[AG]-C [C may be an iron-sulfur ligand] -Sequences known to belong to this class detected by the pattern: ALL, except for Anabaena PCC 7120 and Methanococcus thermolithotrophicus nifK which have Gln instead of the conserved His. -Other sequence(s) detected in Swiss-Prot: 1. -Consensus pattern: [STANQ]-[ET]-C-x(5)-G-D-[DN]-[LIVMT]-x-[STAGR]-[LIVMFYST] [C may be an iron-sulfur ligand] -Sequences known to belong to this class detected by the pattern: ALL, except for nifN proteins. -Other sequence(s) detected in Swiss-Prot: NONE. -Last update: May 2004 / Text revised. [ 1] Pau R.N. "Nitrogenases without molybdenum." Trends Biochem. Sci. 14:183-186(1989). PubMed=2672439 [ 2] Aguilar O.M., Taormino J., Thony B., Ramseier T., Hennecke H., Szalay A.A. "The nifEN genes participating in FeMo cofactor biosynthesis and genes encoding dinitrogenase are part of the same operon in Bradyrhizobium species." Mol. Gen. Genet. 224:413-420(1990). PubMed=2266945 -------------------------------------------------------------------------------- PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see https://prosite.expasy.org/prosite_license.html -------------------------------------------------------------------------------- {END}