Mammalian Enamel Formation

Moradian‐Oldak, Janet; Paine, Michael L.

doi:10.1002/9780470986325.ch15

Cited by 10 publications

(12 citation statements)

References 216 publications

(305 reference statements)

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“…These include a small proteoglycan called biglycan and dentin sialophosphoprotein (DSPP) (2, 25). The latter is mainly expressed by ameloblasts during the early stages of amelogenesis.…”

Section: The Extracellular Protein Matrixmentioning

confidence: 99%

Protein-mediated Enamel Mineralization

2012

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Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principals of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties as well as the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth.

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“…These include a small proteoglycan called biglycan and dentin sialophosphoprotein (DSPP) (2, 25). The latter is mainly expressed by ameloblasts during the early stages of amelogenesis.…”

Section: The Extracellular Protein Matrixmentioning

confidence: 99%

Protein-mediated Enamel Mineralization

2012

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“…The final product is a tissue that is more than 95% mineral by weight with an extraordinary super-structural organization (Robinson et al 1995, Boyde 1989). The complementary crystal maturation and protein degradation that leads to mature enamel involve specific protein-protein, protein-proteinase, and protein-crystal interactions (Smith 1989, Moradian-Oldak and Paine 2008). Three major enamel matrix proteins (amelogenin, ameloblastin, and enamelin) are cleaved by proteinases after they are secreted, and their cleavage products accumulate in specific and deep enamel layers, suggesting that protein proteolysis is necessary for these enamel proteins to perform their functions (Bartlett and Simmer 1999).…”

Section: Introductionmentioning

confidence: 99%

Amelogenin “nanorods” formation during proteolysis by Mmp-20

Yang

Sun

et al. 2011

Journal of Structural Biology

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Amelogenin is cleaved by enamelysin (Mmp-20) soon after its secretion, and the cleavage products accumulate in specific locations during enamel formation, suggesting that parent amelogenin proteolysis is necessary for activating its functions. To investigate the precise roles of Mmp-20 and its influence on the assembly of amelogenin, an in vitro enzymatic digestion process mimicking the initial stages of amelogenin proteolysis was investigated at near-physiological conditions using recombinant porcine amelogenin (rP172) and enamelysin. Hierarchically organized nanorod structures formed during different digestion stages were detected by TEM. At the earliest stage, uniformly dispersed parent amelogenin spherical particles, mixed with some darker stained smaller spheres, and accompanying elongated chain-like nanostructures were observed. Cylindrical nanorods, which appeared to be the result of tight assembly of thin subunit cylindrical discs with thicknesses ranging from ~2.5 nm to ~6.0 nm, were formed after an hour of proteolysis. These subunit building blocks stacked to form nanorods with maximum length of ~100 nm. With the production of more cleavage products, additional morphologies spontaneously evolved from the cylindrical nanorods. Larger ball-like aggregates ultimately formed at the end of proteolysis. The uniform spherical particles, nanorods, morphological patterns evolved from nanorods, and globular aggregated microstructures were successively formed by means of co-assembly of amelogenin and its cleavage products during a comparatively slow proteolysis process. We propose that, following the C-terminal cleavage of amelogenin, co-assembly with its fragments leads to formation of nanorod structures whose properties eventually dictate the super-structural organization of enamel matrix, controlling the elongated growth of enamel apatite crystals.

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“…Tooth enamel is a bioceramic with highly organized hierarchical structures that range from nano to mesoscale levels. The mineralization of enamel takes place in the extracellular space and involves a series of complex cellular and molecular events 1, 2. Protein secretion, supramolecular self‐assembly, protein–mineral interactions and protein degradation are among the most studied 3–6.…”

Section: Introductionmentioning

confidence: 99%

Analysis of secondary structure and self‐assembly of amelogenin by variable temperature circular dichroism and isothermal titration calorimetry

et al. 2009

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Amelogenin is a proline-rich enamel matrix protein known to play an important role in the oriented growth of enamel crystals. Amelogenin self-assembles to form nanospheres and higher order structures mediated by hydrophobic interactions. This study aims to obtain a better insight into the relationship between primary-secondary structure and self-assembly of amelogenin by applying computational and biophysical methods. Variable temperature circular dichroism studies indicated that under physiological pH recombinant full-length porcine amelogenin contains unordered structures in equilibrium with polyproline type II (PPII) structure, the latter being more populated at lower temperatures. Increasing the concentration of rP172 resulted in the promotion of folding to an ordered β-structured assembly. Isothermal titration calorimetry dilution studies revealed that, at all temperatures, self-assembly is entropically driven due to the hydrophobic effect and the molar heat of assembly (ΔH A ) decreases with temperature. Using a computational approach, a profile of domains in the amino acid sequence that have a high propensity to assemble and to have PPII structures has been identified. We conclude that the assembly properties of amelogenin are due to complementarity between the hydrophobic and PPII helix prone regions.

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Mammalian Enamel Formation

Abstract: 508

Cited by 10 publications

References 216 publications

Protein-mediated Enamel Mineralization

Protein-mediated Enamel Mineralization

Amelogenin “nanorods” formation during proteolysis by Mmp-20

Analysis of secondary structure and self‐assembly of amelogenin by variable temperature circular dichroism and isothermal titration calorimetry

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