Four-helix bundle de novo protein

Recently, de novo-synthesized four-helix polypeptides were applied to mimic functions of cytochrome b and to tailor layered cross-linked electrocatalytic electrodes. A four-helix bundle de novo protein (14728 Da) that includes four histidine units in the respective A -helices was assembled on Au electrodes (Figure 22A). Two units of Fe(III)-protoporphyrin IX were reconstituted into the assembly to yield a vectorial electron-transfer cascade [157]. The de novo-synthesized protein assembly forms affinity complexes with the cytochrome-dependent nitrate reductase (NR) and with Co(II) protoporphyrin IX-reconstituted myoglobin [158]. The resulting layered complex of Fe(III) de novo protein-NR or Fe(lll)-de novo protein-Co(II)-reconstituted myoglobin was cross-linked with glutaric dialdehyde to yield electrically contacted electrocatalytic electrodes. The Fe(lll)-de novo protein-NR electrode assembly was applied for the electrocatalyzed reduction NO3 to NOt" and acted as an amperometric sensor (Figure 22B). The Fe(III)-de novo... 

The reconstitution of a tailored de novo protein with Fe(III)-protoporphyrin IX units, (15), on an electrode surface generates a hemoprotcin-type assembly that mimics ET functions of cytochrome c. A four-helix bundle de novo protein, (16), consisting of 128 amino acids and a mass of 14728 was synthesized. It included two pairs of identical helices A and B. The B helices are terminated with Gly-Gly-Cys units for the assembly of the structures on surfaces, whereas the helices A include each two histidines acting as ligand. The position of the histidine ligands on the opposite helices A permits, in principle, the axial ligation of two Fe(III)-heme sites into the protein structure. The four helix-bundle de novo protein was assembled as a monolayer on an Au-electrode as depicted in Fig. 3-16. 

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