1vgi
Crystal structure of xenon bound rat heme-heme oxygenase-1 complex
|
OverviewOverview
Heme oxygenase (HO) catalyzes physiological heme degradation using O(2), and reducing equivalents to produce biliverdin, iron, and CO. Notably, the, HO reaction proceeds without product inhibition by CO, which is generated, in the conversion reaction of alpha-hydroxyheme to verdoheme, although CO, is known to be a potent inhibitor of HO and other heme proteins. In order, to probe how endogenous CO is released from the reaction site, we, collected X-ray diffraction data from a crystal of the CO-bound form of, the ferrous heme-HO complex in the dark and under illumination by a red, laser at approximately 35 K. The difference Fourier map indicates that the, CO ligand is partially photodissociated from the heme and that the, photolyzed CO is trapped in a hydrophobic cavity adjacent to the heme, pocket. This hydrophobic cavity was occupied also by xenon, which is, similar to CO in terms of size and properties. Taking account of the, affinity of CO for the ferrous verdoheme-HO complex being much weaker than, that for the ferrous heme complex, the CO derived from alpha-hydroxyheme, would be trapped preferentially in the hydrophobic cavity but not, coordinated to the iron of verdoheme. This structural device would ensure, the smooth progression of the subsequent reaction, from verdoheme to, biliverdin, which requires O(2) binding to verdoheme.
About this StructureAbout this Structure
1VGI is a Single protein structure of sequence from Rattus norvegicus with HEM, XE and FMT as ligands. Active as Heme oxygenase, with EC number 1.14.99.3 Full crystallographic information is available from OCA.
ReferenceReference
CO-trapping site in heme oxygenase revealed by photolysis of its co-bound heme complex: mechanism of escaping from product inhibition., Sugishima M, Sakamoto H, Noguchi M, Fukuyama K, J Mol Biol. 2004 Jul 30;341(1):7-13. PMID:15312758
Page seeded by OCA on Wed Nov 21 04:49:23 2007