The present invention provides a self assembly molecule having an affinity for one or more target molecules, for use in formation of a heptameric complex, comprising: a) a monomer comprising a multimerization domain of Archaeal Sm1 (AF-Sm1) protein or SM-like ribonucleoprotein from other organisms, able to interact with other molecules of the same monomer comprising a multimerization domain of AF-Sm1 protein or SM-like ribonucleoprotein to self-assemble into a heptamer and b) a target binding domain or peptide attached directly or via a linker to the monomer of (a). Also provided are heptamers comprising these self assembly molecules and methods for their use in therapy, imaging and diagnostics.
