PDBsum entry 2ipf

Oxidoreductase

PDB id: 2ipf

Contents

Protein chains

318 a.a. *

Ligands

NAP ×2

FFA ×2

BME ×6

EDO ×3

TRS

Waters ×692

* Residue conservation analysis

PDB id:

2ipf

Name:

Oxidoreductase

Title:

Crystal structure of 17alpha-hydroxysteroid dehydrogenase in complex with NADP+ and epi-testosterone

Structure:

(3(17)alpha-hydroxysteroid dehydrogenase). Chain: a, b. Engineered: yes

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Gene: akr1c21. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.85Å R-factor: 0.171 R-free: 0.200

Authors:

F.Faucher,L.Cantin,K.Pereira De Jesus-Tran,V.Luu-The,F.Labrie, R.Breton

Key ref:

F.Faucher et al. (2007). Mouse 17alpha-Hydroxysteroid Dehydrogenase (AKR1C21) Binds Steroids Differently from other Aldo-keto Reductases: Identification and Characterization of Amino Acid Residues Critical for Substrate Binding. J Mol Biol, 369, 525-540. PubMed id: 17442338 DOI: 10.1016/j.jmb.2007.03.058

Date:

12-Oct-06 Release date: 19-Jun-07

Protein chains

Q91WR5  (AK1CL_MOUSE) -  Aldo-keto reductase family 1 member C21 from Mus musculus

Seq: 323 a.a.

Struc: 318 a.a.

Enzyme reactions

• Enzyme class: E.C.1.1.1.209 - 3(or 17)alpha-hydroxysteroid dehydrogenase.
• Reaction:
  1. androsterone + NADP⁺ = 5alpha-androstan-3,17-dione + NADPH + H⁺
  2. androsterone + NAD⁺ = 5alpha-androstan-3,17-dione + NADH + H⁺

androsterone (Bound ligand (Het Group name = FFA) corresponds exactly) + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = 5alpha-androstan-3,17-dione + NADPH + H(+)

androsterone (Bound ligand (Het Group name = FFA) corresponds exactly) + NAD(+) (Bound ligand (Het Group name = NAP) matches with 91.67% similarity) = 5alpha-androstan-3,17-dione + NADH + H(+)

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

reference

DOI no: 10.1016/j.jmb.2007.03.058

J Mol Biol 369:525-540 (2007)

PubMed id: 17442338

Mouse 17alpha-Hydroxysteroid Dehydrogenase (AKR1C21) Binds Steroids Differently from other Aldo-keto Reductases: Identification and Characterization of Amino Acid Residues Critical for Substrate Binding.

F.Faucher, L.Cantin, K.Pereira de Jésus-Tran, M.Lemieux, V.Luu-The, F.Labrie, R.Breton.

ABSTRACT

The mouse 17alpha-hydroxysteroid dehydrogenase (m17alpha-HSD) is the unique known member of the aldo-keto reductase (AKR) superfamily able to catalyze efficiently and in a stereospecific manner the conversion of androstenedione (Delta4) into epi-testosterone (epi-T), the 17alpha-epimer of testosterone. Structural and mutagenic studies had already identified one of the residues delineating the steroid-binding cavity, A24, as the major molecular determinant for the stereospecificity of m17alpha-HSD. We report here a ternary complex crystal structure (m17alpha-HSD:NADP(+):epi-T) determined at 1.85 A resolution that confirms this and reveals a unique steroid-binding mode for an AKR enzyme. Indeed, in addition to the interactions found in all other AKRs (van der Waals contacts stabilizing the core of the steroid and the hydrogen bonds established at the catalytic site by the Y55 and H117 residues with the oxygen atom of the ketone group to be reduced), m17alpha-HSD establishes with the other extremity of the steroid nucleus an additional interaction involving K31. By combining direct mutagenesis and kinetic studies, we found that the elimination of this hydrogen bond did not affect the affinity of the enzyme for its steroid substrate but led to a slight but significant increase of its catalytic efficiency (k(cat)/K(m)), suggesting a role for K31 in the release of the steroidal product at the end of the reaction. This previously unobserved steroid-binding mode for an AKR is similar to that adopted by other steroid-binding proteins, the hydroxysteroid dehydrogenases of the short-chain dehydrogenases/reductases (SDR) family and the steroid hormone nuclear receptors. Mutagenesis and structural studies made on the human type 3 3alpha-HSD, a closely related enzyme that shares 73% amino acids identity with the m17alpha-HSD, also revealed that the residue at position 24 of these two enzymes directly affects the binding and/or the release of NADPH, in addition to its role in their 17alpha/17beta stereospecificity.

Selected figure(s)

Figure 1.

Figure 6.
Figure 6. Comparison of the steroid-binding cavity of the m17α-HSD with the more spacious one of the h3α-HSD3. Superposition of the residues making the hydrophobic contacts between the enzyme and the steroid (m17α-HSD with epi-T (in standard CPK color set) and h3α-HSD3 with T (in orange)). Except for the position 24, the side-chain of the residues in the m17α-HSD are generally much bulkier than residues at the same position in the h3α-HSD3 structure. Residues of the m17α-HSD enzyme are identified with the one letter code and the corresponding residue in the h3α-HSD3 sequence is in parenthesis when it differs. The Figure was generated with Pymol (DeLano Scientific).

The above figures are reprinted by permission from Elsevier: J Mol Biol (2007, 369, 525-540) copyright 2007.

Figures were selected by an automated process.