Proteins use a few redox active cofactors, such as hemes quinones, flavins, iron-sulfur clusters and chlorophylls, to carry out a wide range of redox reactions. Proteins modulate cofactor Ems and pKas locally by changing cofactor ring substituents, ligands to metal sites or hydrogen bonding partners. Their electrochemistry is also modified by longer-range electrostatic interactions.  Moving a charged molecule out of water destabilizes it relative to the neutral state.  However proteins are rich in local dipoles that can stabilize buried charges.  Also, ~25% of the amino acids in an average protein are acidic or basic.  If these remain charged throughout a redox reaction they tune electrochemistry by charge-charge interactions.  Redox reactions can shift residues pKas to couple proton and electron transfers.  It will be described how protein-cofactor interactions determine the reaction pathways in multi-cofactor proteins and the sequence of electron and proton transfers in multistep redox reactions.  Supported by NSF-MCB-1022208.

How proteins control tunneling pathways by tuning cofactor electrochemistry

241st National Meeting (2011)

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