PDBsum entry 1bl9

Oxidoreductase

PDB id: 1bl9

Contents

Protein chains

537 a.a. *

Ligands

HEC ×2

DHE ×2

_OH

Waters ×78

* Residue conservation analysis

PDB id:

1bl9

Name:

Oxidoreductase

Title:

Conformational changes occurring upon reduction in nitrite reductase from pseudomonas aeruginosa

Structure:

Nitrite reductase. Chain: a, b. Other_details: d1 heme of subunit b has an hydroxide ion as an axial ligand

Source:

Pseudomonas aeruginosa. Organism_taxid: 287. Atcc: nctc 6750. Collection: nctc 6750. Cellular_location: periplasmic space

Biol. unit:

Homo-Dimer (from PDB file)

Resolution:

2.90Å R-factor: 0.211 R-free: 0.233

Authors:

D.Nurizzo,C.Cambillau,M.Tegoni

Key ref:

D.Nurizzo et al. (1998). Conformational changes occurring upon reduction and NO binding in nitrite reductase from Pseudomonas aeruginosa. Biochemistry, 37, 13987-13996. PubMed id: 9760233 DOI: 10.1021/bi981348y

Date:

20-Jul-98 Release date: 27-Apr-99

Protein chains

P24474  (NIRS_PSEAE) -  Nitrite reductase from Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)

Seq: 568 a.a.

Struc: 537 a.a.

Enzyme reactions

• Enzyme class 2: E.C.1.7.2.1 - nitrite reductase (NO-forming).
• Reaction: nitric oxide + Fe(III)-[cytochrome c] + H2O = Fe(II)-[cytochrome c] + nitrite + 2 H⁺

nitric oxide + Fe(III)-[cytochrome c] + H2O (Bound ligand (Het Group name = HEC) matches with 63.64% similarity) = Fe(II)-[cytochrome c] + nitrite + 2 × H(+)

• Cofactor: Cu cation or Fe cation; FAD
• Enzyme class 3: E.C.1.7.99.1 - hydroxylamine reductase.
• Reaction: A + NH4⁺ + H2O = hydroxylamine + AH2 + H⁺
• Cofactor: Flavoprotein

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi981348y

Biochemistry 37:13987-13996 (1998)

PubMed id: 9760233

Conformational changes occurring upon reduction and NO binding in nitrite reductase from Pseudomonas aeruginosa.

D.Nurizzo, F.Cutruzzolà, M.Arese, D.Bourgeois, M.Brunori, C.Cambillau, M.Tegoni.

ABSTRACT

Nitrite reductase (NiR) from Pseudomonas aeruginosa (EC 1.9.3.2) (NiR-Pa) is a soluble enzyme catalyzing the reduction of nitrite (NO2-) to nitric oxide (NO). The enzyme is a 120 kDa homodimer, in which each monomer carries one c and one d1 heme. The oxidized and reduced forms of NiR from Paracoccus denitrificans GB17 (previously called Thiosphaera pantotropha) (NiR-Pd) have been described [Fülop, V., et al. (1995) Cell 81, 369-377; Williams, P. A., et al. (1997) Nature 389, 406-412], and we recently reported on the structure of oxidized NiR-Pa at 2.15 A [Nurizzo, D., et al. (1997) Structure 5, 1157-1171]. Although the domains carrying the d1 heme are almost identical in both NiR-Pa and NiR-Pd oxidized and reduced structures, the c heme domains show a different pattern of c heme coordination, depending on the species and the redox state. The sixth d1 heme ligand in oxidized NiR-Pd was found to be Tyr25, whereas in NiR-Pa, the homologuous Tyr10 does not interact directly with Fe3+, but via a hydroxide ion. Furthermore, upon reduction, the axial ligand of the c heme of NiR-Pd changes from His17 to Met108. Finally, in the oxidized NiR-Pa structure, the N-terminal stretch of residues (1-29) of one monomer interacts with the other monomer (domain swapping), which does not occur in NiR-Pd. Here the structure of reduced NiR-Pa is described both in the unbound form and with the physiological product, NO, bound at the d1 heme active site. Although both structures are similar to that of reduced NiR-Pd, significant differences with respect to oxidized NiR-Pd were observed in two regions: (i) a loop in the c heme domain (residues 56-62) is shifted 6 A away and (ii) the hydroxide ion, which is the sixth coordination ligand of the heme, is removed upon reduction and NO binding and the Tyr10 side chain rotates away from the position adopted in the oxidized form. The conformational changes observed in NiR-Pa as the result of reduction are less extensive than those occurring in NiR-Pd. Starting with oxidized structures that differ in many respects, the two enzymes converge, yielding reduced conformations which are very similar to each other, which indicates that the conformational changes involved in catalysis are considerably diverse.