Design of electron conductive protein-protein interfaces and redox-active multiprotein assemblies

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This project aims at designing artificial protein interfaces using metals as binding agent between proteins. This should lead to stable protein-protein complexes and at the same time to electron conductivity between the reduction/oxidation sites in the centre of the complexed proteins via the metal at the interface. To allow for reduction/oxidation of the interfacial metals, three different metals in the form of copper ions, iron ions as central atom in heme cofactors and iron/sulfur clusters of the [4Fe4S] type shall be tested, as these are the major agents of metal-based biological electron transfer capability in nature.Each of these conductive elements needs a different and highly specialized protein binding site, which will be designed with computational tools, before the resulting proteins will be produced using Escherichia coli and purified ex vitro. Subsequently the formation of protein-protein complexes and reduction/oxidation activity will be investigated upon addition of the respective metal/metal-cofactor. Once one of the three approaches is successful in generating protein dimers with electron conductivity over the protein-protein interface, the method will be expanded to the self-assembly of larger arrays. For other proteins with non-condcutive metals, the formation of highly ordered arrays of several thousand proteins reaching µm sized sheets by using several protein binding sites in proper orientation towards each other has already been demonstrated.Since electron consuming or electron discharging reactions catalyzed by highly specialized enzymes are of biotechnological interest, the coupling of these reactions to either electrodes or other enzymes, which can consume cheap substrates like hydrogen or even light, is an important goal in biochemistry. However, methods to "wire" proteins together are not well developed and shall thus be established in this project.Larger conductive assemblies of proteins can serve as research tools in the future to understand longer-range electron transfer in nature and might be developed into valuable biological building blocks for electric circuits on a nm to µm scale.