Link protein cDNA sequence reveals a tandemly repeated protein structure.

Link protein stabilizes the cartilage proteoglycan/hyaluronic acid aggregate by binding to both components. We screened a cDNA library prepared from rat chondrosarcoma mRNA in the lambda gt11 expression vector with monoclonal antibodies and polyclonal antisera to link protein. We obtained a clone for two-thirds of the link protein cDNA and identified it based on its deduced amino acid sequence. There are four RNA transcripts for link protein, ranging from 1.5 to 5.5 kilobases in size. The deduced amino acid sequence for link protein shows two domains of 100 residues each, which share 44% homology; within each domain is a 19-residue stretch 74% homologous with its counterpart. This structure indicates that link protein may have been formed by gene duplication.