Primary structure of tetranectin, a plasminogen kringle 4 binding plasma protein: homology with asialoglycoprotein receptors and cartilage proteoglycan core protein.

Tetranectin binds to plasminogen and to isolated kringle 4 [Clemmensen, I., Petersen, L. C., & Kluft, C. (1986) Eur. J. Biochem. 156, 327-333], apparently to its lysine-binding site. Each of the four identical chains consists of 181 amino acid residues. The three intrachain disulfide bonds connect Cys residues 50-60, 77-176, and 152-168. The tetranectin sequence is homologous (17-24% identical positions) with those parts of the asialoglycoprotein receptor family that are considered to be extracellular. Tetranectin has no structures corresponding to those parts of the receptors considered to be intracellular and membrane anchoring. The sequence of tetranectin is also homologous (22-23% identical positions) with the C-terminal globular domain of the core protein of the cartilage proteoglycan. All six Cys residues in tetranectin are located at positions that are also Cys residues in this proteoglycan. Therefore, a plausible disulfide bond pattern can now be proposed for both the asialoglycoprotein receptors and the C-terminal domain of the proteoglycan core protein. No covalently bound carbohydrate has been found.