PDBsum entry 2q9f

Oxidoreductase

PDB id: 2q9f

Contents

Protein chain

433 a.a. *

Ligands

PO4

HEM

C3S

GOL ×6

Waters ×130

* Residue conservation analysis

PDB id:

2q9f

Name:

Oxidoreductase

Title:

Crystal structure of human cytochrome p450 46a1 in complex with cholesterol-3-sulphate

Structure:

Cytochrome p450 46a1. Chain: a. Fragment: residues 51-500. Synonym: cholesterol 24-hydroxylase, ch24h. Engineered: yes

Source:

Homo sapiens. Human. Gene: cyp46a1, cyp46. Expressed in: escherichia coli.

Resolution:

1.90Å R-factor: 0.183 R-free: 0.216

Authors:

M.A.White,N.V.Mast,E.F.Johnson,C.D.Stout,I.A.Pikuleva

Key ref:

N.Mast et al. (2008). Crystal structures of substrate-bound and substrate-free cytochrome P450 46A1, the principal cholesterol hydroxylase in the brain. Proc Natl Acad Sci U S A, 105, 9546-9551. PubMed id: 18621681 DOI: 10.1073/pnas.0803717105

Date:

12-Jun-07 Release date: 17-Jun-08

Protein chain

Q9Y6A2  (CP46A_HUMAN) -  Cholesterol 24-hydroxylase from Homo sapiens

Seq: 500 a.a.

Struc: 433 a.a.

Enzyme reactions

• Enzyme class: E.C.1.14.14.25 - cholesterol 24-hydroxylase.
• Reaction: cholesterol + reduced [NADPH--hemoprotein reductase] + O2 = (24S)- hydroxycholesterol + oxidized [NADPH--hemoprotein reductase] + H2O + H⁺

cholesterol (Bound ligand (Het Group name = C3S) matches with 87.50% similarity) + reduced [NADPH--hemoprotein reductase] + O2 = (24S)- hydroxycholesterol + oxidized [NADPH--hemoprotein reductase] + H2O + H(+)

• Cofactor: Heme-thiolate

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

Added reference

DOI no: 10.1073/pnas.0803717105

Proc Natl Acad Sci U S A 105:9546-9551 (2008)

PubMed id: 18621681

Crystal structures of substrate-bound and substrate-free cytochrome P450 46A1, the principal cholesterol hydroxylase in the brain.

N.Mast, M.A.White, I.Bjorkhem, E.F.Johnson, C.D.Stout, I.A.Pikuleva.

ABSTRACT

By converting cholesterol to 24S-hydroxycholesterol, cytochrome P450 46A1 (CYP46A1) initiates the major pathway for cholesterol removal from the brain. Two crystal structures of CYP46A1 were determined. First is the 1.9-A structure of CYP46A1 complexed with a high-affinity substrate cholesterol 3-sulfate (CH-3S). The second structure is that of the substrate-free CYP46A1 at 2.4-A resolution. CH-3S is bound in the productive orientation and occupies the entire length of the banana-shaped hydrophobic active-site cavity. A unique helix B'-C loop insertion (residues 116-120) contributes to positioning cholesterol for oxygenation catalyzed by CYP46A1. A comparison with the substrate-free structure reveals substantial substrate-induced conformational changes in CYP46A1 and suggests that structurally distinct compounds could bind in the enzyme active site. In vitro assays were performed to characterize the effect of different therapeutic agents on cholesterol hydroxylase activity of purified full-length recombinant CYP46A1, and several strong inhibitors and modest coactivators of CYP46A1 were identified. Structural and biochemical data provide evidence that CYP46A1 activity could be altered by exposure to some therapeutic drugs and potentially other xenobiotics.

Selected figure(s)

Figure 1.
CYP46A1 active site. (a) The composite-omit 2|F[o]|−|F[c]| electron density map (green mesh) contoured at 1.5σ around the heme (in pink) and CH-3S (in yellow). Amino acid residues (in cyan) within 4 Å of CH-3S are shown. The heme iron and water molecule 732 are represented as big brown and small red spheres, respectively. The oxygen, nitrogen, and sulfur atoms are in red, blue, and orange, respectively. Dashed cyan lines indicate hydrogen bonds. Residues forming a circular scaffold are labeled in red. (b) Enlarged view of the active site around the sulfate anion of CH-3S and (c) in the vicinity of the heme iron. Dashed gray lines connect the C24 and C25 of CH-3S and the heme iron.

Figure 2.
Superposition of CH-3S-bound CYP46A1 structure (colored from blue at the N terminus to red at the C terminus) and vitamin D[3]-bound CYP2R1 structure (in wheat) shown in stereoview. CH-3S and vitamin D[3] are in yellow and cyan, respectively, and heme is in pink in CYP46A1 and in light pink in CYP2R1.

Figures were selected by an automated process.