Flexible Structures of SIBLING Proteins, Bone Sialoprotein, and Osteopontin

• Published in: Biochemical and biophysical research communications Vol. 280; no. 2; pp. 460 - 465
• Main Authors: Fisher, L.W., Torchia, D.A., Fohr, B., Young, M.F., Fedarko, N.S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.01.2001
• Subjects: Amino Acid Sequence; Bone and Bones - chemistry; Bone and Bones - metabolism; bone sialoprotein; chromosome 4; flexible structure; Humans; Integrin-Binding Sialoprotein; Integrins - metabolism; Ligands; Magnetic Resonance Spectroscopy; Models, Biological; Molecular Sequence Data; NMR structure; Osteopontin; Pliability; Protein Binding; Protein Conformation; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Sequence Alignment; Sialoglycoproteins - chemistry; Sialoglycoproteins - metabolism; SIBLING; Solutions; NMR structure; flexible structure; bone sialoprotein; osteopontin; SIBLING
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.2000.4146

Bone sialoprotein (BSP) and osteopontin (OPN) are two members of the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family of genetically related proteins that are clustered on human chromosome 4. We present evidence that this entire family is the result of duplication and subsequent divergent evolution of a single ancient gene. The solution structures of these two post-translationally modified recombinant proteins were solved by one dimensional proton NMR and transverse relaxation times. The polypeptide backbones of both free BSP and OPN rapidly sample an ensemble of conformations consistent with them both being completely unstructured in solution. This flexibility appears to enable these relatively small glycoproteins to rapidly associate with a number of different binding partners including other proteins as well as the mineral phase of bones and teeth. These proteins often function by bridging two proteins of fixed structures into a biologically active complex.