BM-40 (also known as SPARC or osteonectin) is an anti-adhesive secreted glycoprotein involved in tissue remodelling. Apart from an acidic N-terminal segment, BM-40 consists of a follistatin-like (FS) domain and an EF-hand calcium-binding (EC) domain. Here we report the crystal structure at 3 ...
BM-40 (also known as SPARC or osteonectin) is an anti-adhesive secreted glycoprotein involved in tissue remodelling. Apart from an acidic N-terminal segment, BM-40 consists of a follistatin-like (FS) domain and an EF-hand calcium-binding (EC) domain. Here we report the crystal structure at 3.1 A resolution of the FS-EC domain pair of human BM-40. The two distinct domains interact through a small interface that involves the EF-hand pair of the EC domain. Residues implicated in cell binding, inhibition of cell spreading and disassembly of focal adhesions cluster on one face of BM-40, opposite the binding epitope for collagens and the N-linked carbohydrate. The elongated FS domain is structurally related to serine protease inhibitors of the Kazal family. Notable differences are an insertion into the inhibitory loop in BM-40 and a protruding N-terminal beta-hairpin with striking similarities to epidermal growth factor. This hairpin is likely to act as a rigid spacer in proteins containing tandemly repeated FS domains, such as follistatin and agrin, and forms the heparin-binding site in follistatin.
Related Citations:
Structure of a Novel Extracellular Ca(2+)-Binding Module in Bm-40 Hohenester, E., Maurer, P., Hohenadl, C., Timpl, R., Jansonius, J.N., Engel, J. (1996) Nat Struct Biol 3: 67
The C-Terminal Portion of Bm-40 (Sparc/Osteonectin) is an Autonomously Folding and Crystallisable Domain that Binds Calcium and Collagen Iv Maurer, P., Hohenadl, C., Hohenester, E., Gohring, W., Timpl, R., Engel, J. (1995) J Mol Biol 253: 347
The Biology of Sparc, a Protein that Modulates Cell-Matrix Interactions Lane, T.F., Sage, E.H. (1994) FASEB J 8: 163
Organizational Affiliation:
Department of Crystallography, Birkbeck College, London, UK.
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