Perlecan - Structure

Structure

Perlecan consists of a core protein of molecular weight 470 kDa to which three long chains (each approximately 70-100 kDa) of glycosaminoglycans (often heparan sulfate, HS but can be chondroitin sulfate, CS) are attached. The core protein consists of five distinct structural domains. The N-terminal domain I (aa ~1-195) contains attachment sites for HS chains. Although HS chains are not required for correct folding and secretion of the protein, lack of HS or decreased sulfation can decrease perlecan's ability to interact with matrix proteins. Removal of HS chains may affect matrix organization and endothelial barrier function. Domain II comprises four repeats homologous to the ligand-binding portion of the LDL receptor with six conserved cysteine residues and a pentapeptide, DGSDE, which mediates ligand binding by the LDL receptor. Domain III has homology to the domain IVa and IVb of laminin. Domain IV consists of a series of IG modules. The C-terminal Domain V, which has homology to the G domain of the long arm of laminin, is responsible for self-assembly and may be important for basement membrane formation in vivo. Thus, perlecan core protein and HS chains could modulate matrix assembly, cell proliferation, lipoprotein binding and cell adhesion.

A diagram showing the domain structure of perlecan is available here