Versican

Abstract

Versican is a large chondroitin sulphate proteoglycan secreted by fibroblasts. It contains domains that are highly homologous to aggrecan in having a hyaluronan-binding domain at its NH 2 -terminal end and two epidermal growth factor (EGF) repeats, a lectin repeat, and a complement control protein repeat at its COOH-terminal end. It may play a role in intracellular signaling, cell recognition, and connecting extracellular matrix components and cell surface glycoproteins. The versican core protein is highly negatively charged and has a calculated pI of 4.2. The NH 2 -terminal domain is similar to the three-loop structure of link protein and to the link-like sequences of aggrecan. On the COOH-side of the hyaluronan-binding domain is a 200 amino acid domain containing two cysteines and a cluster of glutamic acid residues that may be important in the interaction of versican with hydroxyapatite in bone. The COOH-terminal domain of versican contains two EGF repeats in tandem and sequences homologous to the complement control protein repeats of murine factor H and human C4 binding protein. Versican is present in the culture medium of human IMR-90 lung fibroblasts and it has been purified from this source by ammonium sulphate precipitation and DEAE-cellulose chromatograph.