Rather than focusing on the structural details of a specific natural protein, we are designing general protein structural scaffolds (''maquettes'') to accommodate a variety of functions. Here we will present transmembrane electron transfer via AP6, an amphiphilic tetra-helical maquette that binds up to 6 hemes. We demonstrate that AP6 self-assembles with phospholipids into vesicles. Our stop flow experiments confirm that the AP6 maquette significantly increases the electron transfer rates between oxidizing interior and an external redox mediator dye, as shown below.

T , respectively. No changes in highresolution static crystallographic T(deoxy)-and R(oxy)-quaternary and tertiary structures of Hb and their heme environment, as well as the axial coordination structures of the deoxy-heme (n Fe-His = 215 /cm ) and the oxy-heme (n Fe-O2 = 567 /cm ) in solution, are observed, despite K T and K R values are changed as much as 100-and 2,000-folds, respectively. Thus, the assumption that the low-affinity state is caused by the inter-dimeric salt-bridge-linked constraints, the out-of-plane shift of the heme Fe, and the allosteric core constraint in the T(deoxy)-Hb is no longer valid. Although these constraints are completely absent in R(oxy)-Hb, its O 2 -affinity is modulated as much as 2,000-folds by its interaction with heterotropic effectors. The effector-linked modulation of thermal fluctuation of the protein may be responsible.