Group IX - Tetranectin Family

Sequence alignments: Human Human/Mouse

Group IX domain organizationThe tetranectin group of CTLD-containing secreted proteins has three members in both human and mouse: tetranectin, cartilage-derived C-type lectin, and stem cell growth factor (SCGF).  Each polypeptide has an N-terminal tail rich in charged residues, a central neck region, and a C-terminal CTLD.  The neck region mediates homotrimerization through the formation of a coiled-coil of alpha-helices. 

Tetranectin is found in serum, and is present in the extracellular matrix during development, tissue regeneration and cancer, but not in normal adult tissue.  Lower serum tetranectin and higher matrix tetranectin both correlate with poor cancer prognosis.  The charged tail of tetranectin binds sulphated carbohydrates such as glycosaminoglycans.  The CTLD undergoes structural rearrangements upon calcium binding and in its calcium-free form binds to proteins with kringle domains, such as plasminogen.  By stimulating plasminogen activation, tetranectin may regulate proteolysis of extracellular matrix components in development, tissue remodelling and cancer, and influence the proteolytic activation of proteases and growth factors.  Tetranectin may affect coagulation and angiogenesis through interaction with fibrin and angiostatin (a plasminogen fragment), respectively.  During development, tetranectin stimulates muscle cell differentiation and fibre formation, and promotes bone mineralization.  Tetranectin-deficient mice develop a spinal deformity.  Cartilage-derived C-type lectin is expressed in cartilage, where it may have a role in organizing the extracellular matrix.  SCGF is expressed in skeletal and connective tissues, where it stimulates proliferation and differentiation of haematopoietic precursor cells. 


It is not known if carbohydrate recognition plays a role in the function of tetranectin group proteins.  The CTLDs in these proteins resemble CTLDs of the galactose-binding subtype, but attempts to demonstrate sugar-binding activity have been unsuccessful.








Structure of human tetranectin CTLD and coiled-coil region with bound Ca2+

Ca2+ ions are shown in dark blue.  Protein Data Bank structure ID: 1HTN.


This page last updated:
Wednesday, 01 January 2014
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Kurt Drickamer
Division of Molecular Biosciences
Faculty of Natural Sciences
Imperial College London