Osteopontin (OPN) is a member of the small integrin binding ligand N-linked glycoprotein (SIBLING) family of proteins. The molecular structure of OPN contains unique structural motifs, which mediate cell-matrix and cell–cell signaling through the αvβ integrin family and CD44 receptors in a variety of normal and pathologic processes. Avian fibroblasts simultaneously transformed by v-myc and v-mil(raf) display significantly elevated levels of the transcription factor complex AP-1 which

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... y leads to upregulation of the osteopontin (OPN) encoding gene (OPN). Elevated OPN expression is commonly observed in tumor cells where it plays crucial roles in remodeling processes such as inflammation, bone resorption and tumor progression. OPN belongs to the class of intrinsically unfolded proteins (IUP) with no apparent ordered tertiary structure detectable. Intrinsically unfolded proteins have challenged the structure–function paradigm in current biology, since they are now recognized to play essential roles in transcription, translation and signal transduction pathways. The absence of defined structure allows disordered regions of proteins to acquire a high degree of plasticity but also represents an easy target for misfolding, often leading to disease. NMR is uniquely suited to elucidate the structural and dynamic features of these unfolded states. A combination of 15N-relaxation time measurements, pulsed-field gradient (PFG) diffusion measurements, residual dipolar couplings and paramagnetic relaxation enhancement experiments were applied to characterize the dynamic properties of OPN. This work will address the connection between the molecular structure of Osteopontin and its versatile physiological functions.