PDBsum entry: 1h62

Flavoenzyme

PDB id: 1h62

Contents

Protein chain

364 a.a. *

Ligands

ANB

FMN

Waters ×484

* Residue conservation analysis

PDB id:

1h62

Name:

Flavoenzyme

Title:

Structure of pentaerythritol tetranitrate reductase in complex with 1,4-androstadien-3,17-dione

Structure:

Pentaerythritol tetranitrate reductase. Chain: a. Engineered: yes. Other_details: non-covalently bound flavin mononucleotide

Source:

Enterobacter cloacae. Organism_taxid: 550. Strain: pb2. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.9Å R-factor: 0.194 R-free: 0.232

Authors:

T.M.Barna,P.C.Moody

Key ref:

T.M.Barna et al. (2001). Crystal structure of pentaerythritol tetranitrate reductase: "flipped" binding geometries for steroid substrates in different redox states of the enzyme. J Mol Biol, 310, 433-447. PubMed id: 11428899 DOI: 10.1006/jmbi.2001.4779

Date:

04-Jun-01 Release date: 05-Jul-01

Protein chain

P71278  (P71278_ENTCL) -  Pentaerythritol tetranitrate reductase

Seq: 365 a.a.

Struc: 364 a.a.

 Gene Ontology (GO) functional annotation 

• Biological process: metabolic process (1 term)
• Biochemical function: catalytic activity (3 terms)

DOI no: 10.1006/jmbi.2001.4779

J Mol Biol 310:433-447 (2001)

PubMed id: 11428899

Crystal structure of pentaerythritol tetranitrate reductase: "flipped" binding geometries for steroid substrates in different redox states of the enzyme.

T.M.Barna, H.Khan, N.C.Bruce, I.Barsukov, N.S.Scrutton, P.C.Moody.

ABSTRACT

Pentaerythritol tetranitrate reductase (PETN reductase) degrades high explosive molecules including nitrate esters, nitroaromatics and cyclic triazine compounds. The enzyme also binds a variety of cyclic enones, including steroids; some steroids act as substrates whilst others are inhibitors. Understanding the basis of reactivity with cyclic enones requires structural information for the enzyme and key complexes formed with steroid substrates and inhibitors. The crystal structure of oxidised and reduced PETN reductase at 1.5 A resolution establishes a close structural similarity to the beta/alpha-barrel flavoenzyme, old yellow enzyme. In complexes of oxidised PETN reductase with progesterone (an inhibitor), 1,4-androstadiene-3,17-dione and prednisone (both substrates) the steroids are stacked over the si-face of the flavin in an orientation different from that reported for old yellow enzyme. The specifically reducible 1,2 unsaturated bonds in 1,4-androstadiene-3,17-dione and prednisone are not optimally aligned with the flavin N5 in oxidised enzyme complexes. These structures suggest either relative "flipping" or shifting of the steroid with respect to the flavin when bound in different redox forms of the enzyme. Deuterium transfer from nicotinamide coenzyme to 1,4-androstadiene-3,17-dione via the enzyme bound FMN indicates 1alpha addition at the steroid C2 atom. These studies rule out lateral motion of the steroid and indicate that the steroid orientation is "flipped" in different redox states of the enzyme.

Selected figure(s)

Figure 2.
Figure 2. (a) Superposition of the active site illustrating the conformation and environment of the flavin and the location of small ligands bound close to the pyrimidine subnucleus of the flavin isoalloxazine ring in the oxidised and reduced forms. The oxidised forms have acetate, chloride or thiocyanate bound, the reduced form (shown in blue) has water bound and shown "butterfly" bending of the isoalloxazine ring along the N5-N10 axis, and into the active site. Hydrogen bonds to both the active site histidine residues (181 and 184) are shown as broken lines. The electron density for the acetate ion is shown in (b) and the density for thoicyanate in (c). This Figure was prepared with XTALVIEW[41] and Raster3D. [46]

Figure 4.
Figure 4. Chemical structures of the steroid substrates, products and inhibitors of PETN reductase and nomenclature for atom labelling in a general 3-oxo steroid nucleus.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2001, 310, 433-447) copyright 2001.

Figures were selected by an automated process.