Principles of Bioinorganic Chemistry - 2004

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Principles of Bioinorganic Chemistry - 2004
Note The course seminar presentations will be
held on Sunday, October 31, 2004 beginning at
830 AMin the Bush Room. Please remember that
daylight savings time ends that day.
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Protein Tuning of Metalloprotein Core Function
PRINCIPLES

• Similar groups perform different functions
  depending upon their environment
• Changes in available coordination sites controls
  function
• Redox potentials are tuned by the ligands
  H-bonding, e
• Substrate binding affects the timing of electron
  transfer
• Substrate specificity dictated by a.a. side
  chains in active site
• Multiple prosthetic groups can couple functions

ILLUSTRATIONS

• Sulfite Oxidase
• Nitrogenase
• Cyt. c Oxidase

• Rieske Proteins
• Blue Copper
• Iron-sulfur proteins

• Cytochromes
• Aconitase
• Zinc Proteins

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Axial Ligands in Porphyrins Control Function
Replacement of the axial His by Met allows
cytochrome c to function as a catalyst for H2O2
conversion of PhNMe2 to PhNHMe. Met easily
displaced.
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Aconitase Replacement of the terminal ligand at
a 4Fe-4S cluster site allows catalysis of
isocitrate to citrate.
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The Rieske Center
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Coupled Processes - Sulfite Oxidase
If cleave the enzyme with a protease, can isolate
the Mo domain (non-heme). It will still do its
chemistry, but needs an oxidant like O2 or
Fe(CN)6 3- it will not use cyt cox
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Nitrogenase - The P Cluster
reduced state
oxidized state
bridging
bridging
6-coord. S
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Nitrogenase Fe-Mo Protein
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A Catalyst for N2 to NH3 (Schrock)
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Cytochrome c Oxidase
O2 binds and is reduced at the CuB-heme pair
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Proposed OO Bond Splitting Mechanism
OO bond splitting mechanism in cytochrome
oxidase Margareta R. A. Blomberg, Per E. M.
Siegbahn, Gerald T. Babcock and Mårten Wikström
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5.062, 2004 Finé!