[Todos] Lunes 8 de abril a las 13 hs - Seminarios DQIAQF - INQUIMAE

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Seminarios DQIAQF – INQUIMAE

Lunes 8 de abril a las 13 hs


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

13.00 hs

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 H. DAWSON*

 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.

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)