MODULAR SYNTHESIS OF DE-NOVO DESIGNED METALLOPROTEINS FOR LIGHT-INDUCED ELECTRON-TRANSFER

The design and chemical synthesis of two de novo four-helix bundle pro teins is described; each protein has two bound cofactors. Their constr uction from purified peptides is based on the modular assembly of diff erent amphiphilic helices by chemoselective coupling to a cyclic pepti de template. In the hydrophobic interior of the antiparallel four-heli x bundle these proteins contain a heme in a binding pocket with two li gating histidine residues. A ruthenium-tris(bipyridine) complex is cov alently bound to different positions at the hydrophilic side of one of the heme-binding helices. Laser-induced electron transfer across the varied distance through this helix has been studied and compared with a pathway analysis. The UV-visible, CD, and mass spectra are consisten t with the structure and orientation predetermined by the template.