Matrilin-2 is a component of extracellular filamentous networks. To study the interactions by which it can be integrated into such assemblies, full-length and truncated forms of matrilin-2 were recombinantly expressed in HEK-293 cells and purified from conditioned medium. The recombinant proteins, when used in interaction assays, showed affinity to matrilin-2 itself, but also to other collagenous and non-collagenous extracellular matrix proteins. The interaction between matrilin-2 and collagen I was studied in greater detail and could be shown to occur at distinct sites on the collagen I molecule and to have a K (D) of about 3 x 10(-8) M. Interactions with some non-collagenous protein ligands were even stronger, with matrilin-2 binding to fibrillin-2, fibronectin and laminin-1-nidogen-1 complexes, with K (D) values in the range of 10(-8)-10(-11) M. Co-localization of matrilin-2 with these ligands in the dermal-epidermal basement membrane, in the microfibrils extending from the basement membrane into the dermis, and in the dermal extracellular matrix, indicates a physiological relevance of the interactions in the assembly of supramolecular extracellular matrix structures.