The EF-hand is a highly conserved Ca(2+)-binding motif found in many cytosolic Ca(2+)-modulated proteins. Here we report the crystal structure at 2.0 A resolution of the carboxy-terminal domain of human BM-40 (SPARC, osteonectin), an extracellular matrix protein containing an EF-hand pair ...
The EF-hand is a highly conserved Ca(2+)-binding motif found in many cytosolic Ca(2+)-modulated proteins. Here we report the crystal structure at 2.0 A resolution of the carboxy-terminal domain of human BM-40 (SPARC, osteonectin), an extracellular matrix protein containing an EF-hand pair. The two EF-hands interact canonically but their detailed structures are unusual. In the first EF-hand a one-residue insertion is accommodated by a cis-peptide bond and by substituting a carboxylate by a peptide carbonyl as a Ca2+ ligand. The second EF-hand is stabilized by a disulphide bond. The EF-hand pair interacts tightly with an amphiphilic amino-terminal helix, reminiscent of target peptide binding by calmodulin. The present structure defines a novel protein module occurring in several other extracellular proteins.
Related Citations:
The C-Terminal Portion of Bm-40 (Sparc(Slash)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 Structural Biology, University of Basel, Switzerland.
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