Abstract: A novel family of protein libraries comprising CTLDs (C-type Lectin-Like Domains) in which internal polypeptide loop-regions lining the ligand binding sites in CTLDs have been replaced with ensembles of completely or partially randomised polypeptide segments. Tetranectin CTLDs were chosen as framework for the preferred embodiment of the invention; and versatile phagemid vectors useful in the generation and manipulation of human and murine tetranectin CTLD libraries are disclosed as part of this invention. Tetranectin CTLDs in monomeric as well as in trimeric form are efficiently displayed as gene III fusions in fully functional form by the recombinant fd phage display vector. CTLD derivatives with affinity for new ligands may readily be isolated from libraries of vectors displaying CTLDs, in which loop-regions have been randomised, using one or more rounds of enrichment by screening or selection followed by amplification of the enriched subpopulation in each round.

Abstract: The present invention relates to the design of trimeric polypeptides using polypeptide structural elements derived from the tetranectin protein family, and their use in rational de novo design and production of multi-functional molecules including the application of the multi-functional molecules in protein library technology, such as phage display technology, diagnostic and therapeutic systems, such as human gene therapy and imaging. The trimeric polypeptides being constructed as a monomer polypeptide construct comprising at least one tetranectin trimerising structural element (TTSE) which is covalently linked to at least one heterologous moiety, said TTSE being capable of forming a stable complex with two other TTSEs; or as an oligomer which is comprised of two monomer polypeptide constructs as mentioned above, and which comprises three TTSEs or a multiplum of three TTSEs, or which is comprised of three monomer polypeptide constructs.