Exploiting the concepts learnt from nature to build new nanomaterials from the bottom-up is critical for the efficient design of complex nanodevices. We demonstrate for the first time that the capacity of the a-synuclein protein to assemble into nanofibers can be used for the synthesis of metallic nanowires. Silver and platinum nanowires with controlled diameters, ranging from 15 to 125nm, have been synthesized on an a-synuclein protein fiber scaffold.