2akj
From Proteopedia
|
Structure of spinach nitrite reductase
Overview
The structure of nitrite reductase, a key enzyme in the process of, nitrogen assimilation, has been determined using X-ray diffraction to a, resolution limit of 2.8 A. The protein has a globular fold consisting of 3, alpha/beta domains with the siroheme-iron sulfur cofactor at the interface, of the three domains. The Fe(4)S(4) cluster is coordinated by cysteines, 441, 447, 482, and 486. The siroheme is located at a distance of 4.2 A, from the cluster, and the central iron atom is coordinated to Cys 486. The, siroheme is surrounded by several ionizable amino acid residues that, facilitate the binding and subsequent reduction of nitrite. A model for, the ferredoxin:nitrite reductase complex is proposed in which the binding, of ferredoxin to a positively charged region of nitrite reductase results, in elimination of exposure of the cofactors to the solvent. The structure, of nitrite reductase shows a broad similarity to the hemoprotein subunit, of sulfite reductase but has many significant differences in the backbone, positions that could reflect sequence differences or could arise from, alterations of the sulfite reductase structure that arise from the, isolation of this subunit from the native complex. The implications of the, nitrite reductase structure for understanding multi-electron processes are, discussed in terms of differences in the protein environments of the, cofactors.
About this Structure
2AKJ is a Single protein structure of sequence from Spinacia oleracea with SF4 and SRM as ligands. Active as Ferredoxin--nitrite reductase, with EC number 1.7.7.1 Full crystallographic information is available from OCA.
Reference
Structure of spinach nitrite reductase: implications for multi-electron reactions by the iron-sulfur:siroheme cofactor., Swamy U, Wang M, Tripathy JN, Kim SK, Hirasawa M, Knaff DB, Allen JP, Biochemistry. 2005 Dec 13;44(49):16054-63. PMID:16331965
Page seeded by OCA on Wed Nov 21 08:11:20 2007
