Send to

Choose Destination
See comment in PubMed Commons below
Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13883-8. doi: 10.1073/pnas.0804099105. Epub 2008 Sep 11.

Modes of heme binding and substrate access for cytochrome P450 CYP74A revealed by crystal structures of allene oxide synthase.

Author information

Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.


Cytochrome P450s exist ubiquitously in all organisms and are involved in many biological processes. Allene oxide synthase (AOS) is a P450 enzyme that plays a key role in the biosynthesis of oxylipin jasmonates, which are involved in signal and defense reactions in higher plants. The crystal structures of guayule (Parthenium argentatum) AOS (CYP74A2) and its complex with the substrate analog 13(S)-hydroxyoctadeca-9Z,11E-dienoic acid have been determined. The structures exhibit a classic P450 fold but possess a heme-binding mode with an unusually long heme binding loop and a unique I-helix. The structures also reveal two channels through which substrate and product may access and leave the active site. The entrances are defined by a loop between beta3-2 and beta3-3. Asn-276 in the substrate binding site may interact with the substrate's hydroperoxy group and play an important role in catalysis, and Lys-282 at the entrance may control substrate access and binding. These studies provide both structural insights into AOS and related P450s and a structural basis to understand the distinct reaction mechanism.

[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center