1do4
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CARBONMONOXY-MYOGLOBIN (MUTANT L29W) AFTER PHOTOLYSIS AT T<180K
OverviewOverview
Myoglobin, a small globular haem protein that binds gaseous ligands such, as O2, CO and NO reversibly at the haem iron, serves as a model for, studying structural and dynamic aspects of protein reactions., Time-resolved spectroscopic measurements after photodissociation of the, ligand revealed a complex ligand-binding reaction with multiple kinetic, intermediates, resulting from protein relaxation and movements of the, ligand within the protein. To observe the structural changes induced by, ligand dissociation, we have carried out X-ray crystallographic, investigations of carbon monoxy-myoglobin (MbCO mutant L29W) crystals, illuminated below and above 180 K, complemented by time-resolved infrared, spectroscopy of CO rebinding. Here we show that below 180 K, photodissociated ligands migrate to specific sites within an internal, cavity--the distal haem pocket--of an essentially immobilized, frozen, protein, from where they subsequently rebind by thermally activated, barrier crossing. Upon photodissociation above 180 K, ligands escape from, the distal pocket, aided by protein fluctuations that transiently open, exit channels. We recover most of the ligands in a cavity on the opposite, side of the haem group.
About this StructureAbout this Structure
1DO4 is a Single protein structure of sequence from Physeter catodon with SO4, HEM and CMO as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Ligand binding and conformational motions in myoglobin., Ostermann A, Waschipky R, Parak FG, Nienhaus GU, Nature. 2000 Mar 9;404(6774):205-8. PMID:10724176
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