TSG-6 Transfers Proteins between Glycosaminoglycans via a Ser28-mediated Covalent Catalytic Mechanism

Studies of the interaction between Bikunin proteins, tumor necrosis factor-stimulated gene-6 protein (TSG-6), and glycos-aminoglycans have revealed a unique catalytic activity where TSG-6/heavy chain 2 transfer heavy chain subunits between glycosaminoglycan chains. The activity is mediated by TSG-6/heavy chain 2 and involves a transient SDS stable interaction between TSG-6 and the heavy chain to be transferred. The focus of this study was to characterize the molecular structure of this cross-link to gain further insight into the catalytic mechanism. The result showed that the C-terminal Asp residue of the heavy chains forms an ester bond to Ser(28) carbon of TSG-6 suggesting that this residue plays a role during catalysis.