[Todos] Lunes 8 de abril 13.00hs - Seminarios DQIAQF - INQUIMAE

[Fabio Doctorovich]

Seminarios DQIAQF - INQUIMAE, Lunes 08 de abril - 13 hs.

Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3


Understanding Catalysis by Heme Enzymes Starts with Their Active Site Coordination Structure: Application of Magnetic Circular Dichroism Spectroscopy to the Study of Novel Heme Proteins

John Dawson, University of South Carolina



Magnetic circular dichroism spectroscopy provides diagnostic spectral data sensitive to the identity of the axial ligands and to the spin and oxidation states of heme iron centers in proteins.  In this effort, we have found the proximal ligand His93Gly myoglobin cavity mutant to be a remarkably versatile scaffold for preparation of model heme complexes of defined ligation.  In particular, the difference in accessibility of the two sides of the heme iron center offers the advantage of forming ambient-temperature mixed-ligand heme model complexes, which are very difficult to prepare with model systems in organic solvents.  Moreover, in the H93G Mb system, the protective environment provided by the protein allows for the formation of relatively stable oxyferrous and ferryl [Fe(IV)=O] complexes with variable ligands trans to the normally reactive dioxygen and oxo substituents.  Ferrous, ferric and ferryl His93Gly Mb derivatives with various exogenous ligands have been prepared as models for native heme iron active sites ligated by proximal Lys (amines), Asp or Glu (carboxylates), Tyr (phenols), seleno-Cys (selenols), Cys (thiols) and Met (thioethers).    Building upon this foundation, we have focused our attention on the use of the H93G Mb cavity mutant system to aid our investigation of the coordination structure of novel heme binding and transport proteins and heme-containing oxidative enzymes.  (Funding NIH GM 26730)

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Professor Dawson is Carolina Distinguished Professor and Chair of the Department of Chemistry and Biochemistry at the University of South Carolina with a joint appointment at the School of Medicine.  Educated at Columbia (A.B.) and Stanford (Ph.D.), he was an NIH postdoctoral fellow at CalTech prior to his current appointment.  An award-winning researcher in bioinorganic chemistry, he has been author of over 210 research publications and has given over 320 invited lectures at conferences and universities worldwide.  He is Editor of the Journal of Inorganic Biochemistry, the oldest journal focused exclusively on bioinorganic chemistry. 
He is best known for his investigations into the active site structures and mechanisms of action of cytochrome P450 and of novel halogenating and dehalogenating peroxidases.  His research has also demonstrated the importance of magnetic circular dichroism spectroscopy in establishing the coordination structures of heme centers in proteins.    


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