Abstract: The present invention relates to a trimeric fusion protein comprising three polypeptide chains, wherein each polypeptide chain comprises a eukaryotic collagen or collagen-like domain and a prokaryotic or viral trimerisation domain (PVTD). Also provided is a fusion polypeptide comprising a eukaryotic collagen or collagen-like domain and a PVTD. A suitable PVTD of a fusion polypeptide or protein of the invention is preferably derived from a collagen-like protein sequence found in the genome of the E. coli strain O157:H7 and other E. coli strains, and in bacteriophages or prophages infecting these strains or embedded in their genomes. A PVTD mediates trimerisation of collagen or collagen like polypeptides.