The enormous potential of proteins as molecular components of nanodevices and smart materials has been heralded for some time, but successful examples of designed protein nanostructures remain scarce. This is in part due to the paucity of generic building blocks that can be manipulated to build structures of choice. Here we highlight doughnut-shaped proteins as new building blocks, and results showing that their supramolecular assembly can be controlled by a combination of site-directed mutagenesis and environmental triggers. In particular, we present data to show that peroxiredoxin proteins assemble in response to a redox trigger, pH and designed peptides, and that these transitions vary according to specific site-directed mutations at key interfaces. We also demonstrate that Lsm proteins can assemble into previously unobserved supramolecular assemblies in response to a metal ion trigger. Overall, these systems show promise as components for designer nanostructures.