Supramolecular polymer formation by a de novo hemoprotein with a synthetic diheme compound

Proteins are attractive materials for supramolecular chemistry due to their multifunctionality and self-organization ability. In this work, we synthesized a diheme compound, in which two iron-protoporphyrin IX molecules are associated via a linker chain, and introduced it into a de novo designed four-helix bundle protein with two heme-binding sites. The protein gradually bound the diheme compound by bis-histidyl ligation and formed supramolecular polymers. Polymer formation was observed by atomic force microscopy (AFM), which revealed the highly branched, dendritic forms of the fibrous architecture. The present results may open a pathway toward nanowire construction with de novo heme-proteins.