The present invention provides an engineered multidomain protein including at least two nonidentical engineered domains, each of which contains a protein-protein interaction interface containing amino acid sequence segments derived from two or more existing homologous parent domains, thereby conferring on the engineered domains assembly specificities distinct from assembly specificities of the parent domains. In particular, the engineered domains form heterodimers with one another preferentially over forming homodimers. Methods of designing and using the engineered proteins are also included.
