Dentin phosphoprotein sequence motifs and molecular modeling: conformational adaptations to mineral crystals

Dahlin, Stefan; Ångström, Jonas; Linde, Anders

doi:10.1111/j.1600-0722.1998.tb02182.x

Cited by 27 publications

(20 citation statements)

References 26 publications

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“…Energy minimization has also been used to model the adsorption to HA of phosphopeptides typical of mineralized-tissue proteins. Oligomers containing phosphoserine-aspartic acid dipeptides were reported to interact favourably with {001} faces of HA [63]. However, a pentapeptide of phosphoserine and glutamic acid was found to adsorb to {010} and {100} faces in preference to {001} faces [36].…”

Section: Discussionmentioning

confidence: 99%

Roles of Electrostatics and Conformation in Protein-Crystal Interactions

et al. 2010

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In vitro studies have shown that the phosphoprotein osteopontin (OPN) inhibits the nucleation and growth of hydroxyapatite (HA) and other biominerals. In vivo, OPN is believed to prevent the calcification of soft tissues. However, the nature of the interaction between OPN and HA is not understood. In the computational part of the present study, we used molecular dynamics simulations to predict the adsorption of 19 peptides, each 16 amino acids long and collectively covering the entire sequence of OPN, to the {100} face of HA. This analysis showed that there is an inverse relationship between predicted strength of adsorption and peptide isoelectric point (P<0.0001). Analysis of the OPN sequence by PONDR (Predictor of Naturally Disordered Regions) indicated that OPN sequences predicted to adsorb well to HA are highly disordered. In the experimental part of the study, we synthesized phosphorylated and non-phosphorylated peptides corresponding to OPN sequences 65–80 (pSHDHMDDDDDDDDDGD) and 220–235 (pSHEpSTEQSDAIDpSAEK). In agreement with the PONDR analysis, these were shown by circular dichroism spectroscopy to be largely disordered. A constant-composition/seeded growth assay was used to assess the HA-inhibiting potencies of the synthetic peptides. The phosphorylated versions of OPN65-80 (IC50 = 1.93 µg/ml) and OPN220-235 (IC50 = 1.48 µg/ml) are potent inhibitors of HA growth, as is the nonphosphorylated version of OPN65-80 (IC50 = 2.97 µg/ml); the nonphosphorylated version of OPN220-235 has no measurable inhibitory activity. These findings suggest that the adsorption of acidic proteins to Ca2+-rich crystal faces of biominerals is governed by electrostatics and is facilitated by conformational flexibility of the polypeptide chain.

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Section: Discussionmentioning

confidence: 99%

Roles of Electrostatics and Conformation in Protein-Crystal Interactions

et al. 2010

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“…A biological template with epitaxial match to the crystal surface could provide such a driving force. In the case of PP, calcium-mediated self-assembly of extended (DS*S*) n / (DS*) m chain (S* represents phosphoserine) forms a periodic polyelectrolyte template presenting a well-spaced array of carboxyl and phosphate groups, with potential epitaxial match to the apatite surface, thereby facilitating apatite crystallization [Dahlin et al, 1998]. …”

Section: Discussionmentioning

confidence: 99%

Role of Phosphophoryn in Dentin Mineralization

George

Hao

2005

Cells Tissues Organs

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Mineral deposition is essential for the development of hard tissues like bone and teeth. In matrix-mediated mechanisms responsible for dentin formation, type I collagen defines the framework for mineral deposition and by itself is not sufficient to support nucleation of hydroxyapatite. However, in the presence of non-collagenous proteins, nucleation sites have been identified within the hole regions of the fibrils, and at these sites, mineral crystals can grow and propagate. Non-collagenous proteins constitute 5–10% of the total extracellular matrix proteins. They are embedded within the mineral deposits, suggesting a possible interaction with the mineral phase. During dentin formation, phosphophoryn (PP), an abundant macromolecule in the extracellular matrix, can initiate mineral deposition in localized regions by matrix-mediated mineralization mechanism. In our work, we have demonstrated that PP, due to its highly phosphorylated post-translational modification, can bind calcium ions with high affinity and at the same time aggregate collagen fibrils at the mineralization front. Molecular modeling has further demonstrated that the spacing of the carboxyl and phosphate groups present on PP might be essential for dictating the crystal orientation relative to the collagen substrate. Thus, PP may provide the interface linkage between mineral crystal and collagen fibrils.

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“…The (S*D) m domains have different phosphate and carboxylate orientations and thus different calcium ion and apatite surface binding properties. The arrays of negatively charged anions along the backbone potentially may have an expitaxial match to the hydroxyapatite crystal surface (10,11).…”

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confidence: 99%

Phosphorylation of Phosphophoryn Is Crucial for Its Function as a Mediator of Biomineralization

Ramachandran

Dahl

et al. 2005

Journal of Biological Chemistry

161

157

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Phosphoproteins of the organic matrix of bone and dentin have been implicated as regulators of the nucleation and growth of the inorganic Ca-P crystals of vertebrate bones and teeth. One such protein identified in the dentin matrix is phosphophoryn (PP). It is highly acidic in nature because of a high content of aspartic acid and phosphate groups on serines. The 244-residue carboxyl-terminal domain of rat PP, predominantly containing the aspartic acid-serine repeats, has been cloned, and the corresponding protein has been expressed recombinantly in Escherichia coli. This portion of PP, named DMP2 (dentin matrix protein 2), is not phosphorylated by the bacteria and thus provided a means to study the function of the phosphate groups, the major post-translational modification of native PP. The recombinant DMP2 (rDMP2) possessed much lower calcium binding capacity than native PP. Small angle x-ray scattering experiments demonstrated that PP folds to a compact globular structure upon calcium binding, whereas rDMP2 maintained an unfolded structure. In vitro nucleation experiments showed that PP could nucleate plate-like apatite crystals in pseudophysiological buffer, whereas rDMP2 failed to mediate the transformation of amorphous calcium phosphate to apatite crystals under the same experimental conditions. Collagen binding experiments demonstrated that PP favors the formation of collagen aggregates, whereas in the presence of rDMP2 thin fibrils are formed. Overall these results suggested that the phosphate moieties in phosphophoryn are important for its function as a mediator of dentin biomineralization.Mineralization is an essential requirement for the development of the mechanical properties of hard tissues such as bones and teeth. However, on a volume basis, the mineral constitutes only about 50% of a bone; the remaining extracellular organic matrix (ECM) 2 is a hydrated mixture of collagen and noncollagenous matrix proteins (NCPs). The NCPs constitute 5-10% of the total ECM and are associated with the mineral phase so strongly that the tissues need to be demineralized before those proteins can be extracted. The NCPs are mostly acidic proteins, rich in glutamic acid, aspartic acid, and phosphorylated serine/threonine residues, with a high capacity for binding calcium ions and hydroxyapatite crystal surfaces. Therefore, they have been implicated in the regulation of mineral deposition during osteogenesis and dentinogenesis (1). Phosphorylation of threonine and serine residues takes place as a post-translational modification of the core protein via the action of casein kinases (2). found that dentin mineralization was impaired in the presence of casein kinase inhibitors. Thus post-translational phosphorylation of NCPs is crucial for biomineralization.The major phosphoprotein of dentin is the Asp-and Ser-rich protein called phosphophoryn. The name phosphophoryn (PP) was coined to describe its exceedingly high content of phosphate groups. PP, as isolated from dentin, has a unique composition with aspartyl and seryl ...

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Dentin phosphoprotein sequence motifs and molecular modeling: conformational adaptations to mineral crystals

Cited by 27 publications

References 26 publications

Roles of Electrostatics and Conformation in Protein-Crystal Interactions

Roles of Electrostatics and Conformation in Protein-Crystal Interactions

Role of Phosphophoryn in Dentin Mineralization

Phosphorylation of Phosphophoryn Is Crucial for Its Function as a Mediator of Biomineralization

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