A multilevel biomemory device displays two pairs of nonvolatile write, read, and erase functions (see figure). The device consists of recombinant azurin/cytochrome c. Azurin is recombined with a cysteine residue to enhance the stability of the self-assembled protein on a gold surface. Then, cytochrome c is adsorbed onto the immobilized azurin layer. The verified memory characteristic of the proposed device implies that the metallo-protein is a very promising molecule for the development of a new type of memory device.