|Name||Mr. Ruipeng Lei|
|Organization or Institution||Florida International University|
Distinct mechanism of oxygen and carbon monoxide interactions with heme protein
Jaroslava Miksovska1, Ruipeng Lei1, Sophie Bernad2, Valerie Derrien3
1 Chemistry, Florida International University, Miami, FL, USA, 2 Chemistry, University of Paris XI Orsay, Orsay, France, 3 Universityof Paris XI Orsay, Orsay, France.
Interactions of heme proteins with gaseous ligands (CO and O2) have been characterized to provide insight into the structure function relationship in various heme protein with CO being often used as a model compound due to the stability of the Fe(II)-CO complexes towards oxidation. Here we have used photoacoustic calorimetry to determine the thermodynamic profiles for O2 photo-dissociation from several heme proteins (human hemoglobin, rise hemoglobin, neuroglobin and cytoglobin ) and compare them to the thermodynamic profiles for CO photo-release. Our data indicate a distinct structural changes in terms of reaction volume and enthalpy changes association with the transition between the oxygen bound, six-coordinate heme protein and ligand free, five-coordinate protein. Interestingly, thermodynamic parameters for O2 release from human hemoglobin and neuroglobin demonstrate a strong temperature dependence that has not been observed for the CO photorelease. These results are discussed in term of the role of distal histidine and a hydrogen bond network involving the heme propionate groups and surrounding amino acid residues in modulating energetics and dynamics of structural changes in heme proteins.