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Zhao H, Zhang Q, Chu J. Effect of phosphate group on remineralization of early enamel caries regulated by amelogenin peptide. PLoS One 2024; 19:e0303147. [PMID: 38771806 PMCID: PMC11108222 DOI: 10.1371/journal.pone.0303147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 04/20/2024] [Indexed: 05/23/2024] Open
Abstract
OBJECTIVE To show the effect of the phosphate group on the remineralization process of early enamel caries mediated by amelogenin peptide. METHODS Freshly extracted, completed, and crack-free bovine teeth were used to create artificial early enamel caries, which were randomly divided into four groups: Group A: fluorination remineralized solution treatment group; Group B: pure remineralized solution treatment group. Group C: 100 g/ml recombinant Amelogenin peptide remineralized solution treatment group (with single phosphate group on N-terminus); Group D: 100 g/ml non-phosphorylated recombinant Amelogenin peptide remineralized solution treatment group (without single phosphate group on N-terminus). For 12 days, fresh remineralized solutions were replaced daily. Transverse microradiography (TMR) was used after remineralization to determine mineral loss and demineralization depth before and after each sample's remineralization. Each sample's depth of remineralization and mineral acquisition were then determined. RESULTS The recombinant amelogenin peptide group significantly outperformed the non-phosphorylated amelogenin peptide group in terms of mineral acquisition and mineralization depth (P<0.05). CONCLUSIONS The recombinant Amelogenin's solitary phosphate group at the N-terminus helps recombinant Amelogenin to encourage the remineralization process of early enamel caries.
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Affiliation(s)
- Hualei Zhao
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- Zhengzhou Stomatological Hospital, Zhengzhou, China
| | - Qun Zhang
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Jinpu Chu
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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2
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Toke O. Three Decades of REDOR in Protein Science: A Solid-State NMR Technique for Distance Measurement and Spectral Editing. Int J Mol Sci 2023; 24:13637. [PMID: 37686450 PMCID: PMC10487747 DOI: 10.3390/ijms241713637] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/30/2023] [Accepted: 09/01/2023] [Indexed: 09/10/2023] Open
Abstract
Solid-state NMR (ss-NMR) is a powerful tool to investigate noncrystallizable, poorly soluble molecular systems, such as membrane proteins, amyloids, and cell walls, in environments that closely resemble their physical sites of action. Rotational-echo double resonance (REDOR) is an ss-NMR methodology, which by reintroducing heteronuclear dipolar coupling under magic angle spinning conditions provides intramolecular and intermolecular distance restraints at the atomic level. In addition, REDOR can be exploited as a selection tool to filter spectra based on dipolar couplings. Used extensively as a spectroscopic ruler between isolated spins in site-specifically labeled systems and more recently as a building block in multidimensional ss-NMR pulse sequences allowing the simultaneous measurement of multiple distances, REDOR yields atomic-scale information on the structure and interaction of proteins. By extending REDOR to the determination of 1H-X dipolar couplings in recent years, the limit of measurable distances has reached ~15-20 Å, making it an attractive method of choice for the study of complex biomolecular assemblies. Following a methodological introduction including the most recent implementations, examples are discussed to illustrate the versatility of REDOR in the study of biological systems.
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Affiliation(s)
- Orsolya Toke
- Laboratory for NMR Spectroscopy, Structural Research Centre, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
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3
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Buchko GW, Zhou M, Vesely CH, Tao J, Shaw WJ, Mehl RA, Cooley RB. High-yield recombinant bacterial expression of 13 C-, 15 N-labeled, serine-16 phosphorylated, murine amelogenin using a modified third generation genetic code expansion protocol. Protein Sci 2023; 32:e4560. [PMID: 36585836 PMCID: PMC9850436 DOI: 10.1002/pro.4560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/21/2022] [Accepted: 12/29/2022] [Indexed: 01/01/2023]
Abstract
Amelogenin constitutes ~90% of the enamel matrix in the secretory stage of amelogenesis, a still poorly understood process that results in the formation of the hardest and most mineralized tissue in vertebrates-enamel. Most biophysical research with amelogenin uses recombinant protein expressed in Escherichia coli. In addition to providing copious amounts of protein, recombinant expression allows 13 C- and 15 N-labeling for detailed structural studies using NMR spectroscopy. However, native amelogenin is phosphorylated at one position, Ser-16 in murine amelogenin, and there is mounting evidence that Ser-16 phosphorylation is important. Using a modified genetic code expansion protocol we have expressed and purified uniformly 13 C-, 15 N-labeled murine amelogenin (pS16M179) with ~95% of the protein being correctly phosphorylated. Homogeneous phosphorylation was achieved using commercially available, enriched, 13 C-, 15 N-labeled media, and protein expression was induced with isopropyl β-D-1-thiogalactopyranoside at 310 K. Phosphoserine incorporation was verified from one-dimensional 31 P NMR spectra, comparison of 1 H-15 N HSQC spectra, Phos-tag SDS PAGE, and mass spectrometry. Phosphorus-31 NMR spectra for pS16M179 under conditions known to trigger amelogenin self-assembly into nanospheres confirm nanosphere models with buried N-termini. Lambda phosphatase treatment of these nanospheres results in the dephosphorylation of pS16M179, confirming that smaller oligomers and monomers with exposed N-termini are in equilibrium with nanospheres. Such 13 C-, 15 N-labeling of amelogenin with accurately encoded phosphoserine incorporation will accelerate biomineralization research to understand amelogenesis and stimulate the expanded use of genetic code expansion protocols to introduce phosphorylated amino acids into proteins.
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Affiliation(s)
- Garry W. Buchko
- Earth and Biological Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA,School of Molecular BiosciencesWashington State UniversityPullmanWashingtonUSA
| | - Mowei Zhou
- Earth and Biological Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Cat Hoang Vesely
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
| | - Jinhui Tao
- Physical and Computational Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Wendy J. Shaw
- Physical and Computational Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Ryan A. Mehl
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
| | - Richard B. Cooley
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
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4
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Tao J, Hanson E, Dohnalkova AC, Buchko GW, Jin B, Shaw WJ, Tarasevich BJ. Changes in the C-terminal, N-terminal, and histidine regions of amelogenin reveal the role of oligomer quaternary structure on adsorption and hydroxyapatite mineralization. Front Physiol 2022; 13:1034662. [PMID: 36523551 PMCID: PMC9746691 DOI: 10.3389/fphys.2022.1034662] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/14/2022] [Indexed: 10/29/2023] Open
Abstract
Adsorption interactions between amelogenin and calcium phosphate minerals are believed to be important to amelogenin's function in enamel formation, however, the role of specific amino acid residues and domains within the protein in controlling adsorption is not well known. We synthesized "mechanistic probes" by systematically removing charged regions of amelogenin in order to elucidate their roles. The probes included amelogenin without the charged residues in the N-terminus (SEKR), without two, three, or eight histidines (H) in the central protein region (H2, H3, H8), or without the C-terminal residues (Delta). In-situ atomic force microscopy (AFM) adsorption studies onto hydroxyapatite (HAP) single crystals confirmed that the C-terminus was the dominant domain in promoting adsorption. We propose that subtle changes in protein-protein interactions for proteins with histidines and N-terminal residues removed resulted in changes in the oligomer quaternary size and structure that also affected protein adsorption. HAP mineralization studies revealed that the oligomer-HAP binding energy and protein layer thickness were factors in controlling the amorphous calcium phosphate (ACP) to HAP induction time. Our studies with mechanistic probes reveal the importance of the oligomer quaternary structure in controlling amelogenin adsorption and HAP mineralization.
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Affiliation(s)
- Jinhui Tao
- Pacific Northwest National Laboratory, Richland, WA, United States
| | - Emma Hanson
- Pacific Northwest National Laboratory, Richland, WA, United States
| | | | - Garry W. Buchko
- Pacific Northwest National Laboratory, Richland, WA, United States
- School of Molecular Biosciences, Washington State University, Pullman, WA, United States
| | - Biao Jin
- Pacific Northwest National Laboratory, Richland, WA, United States
| | - Wendy J. Shaw
- Pacific Northwest National Laboratory, Richland, WA, United States
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5
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Holzinger J, Kotisch H, Richter KW, Konrat R. Binding Mode Characterization of Osteopontin on Hydroxyapatite by Solution NMR Spectroscopy. Chembiochem 2021; 22:2300-2305. [PMID: 33914399 PMCID: PMC8359842 DOI: 10.1002/cbic.202100139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/28/2021] [Indexed: 01/13/2023]
Abstract
Extracellular matrix glycoproteins play a major role in bone mineralization and modulation of osteogenesis. Among these, the intrinsically disordered protein osteopontin (OPN) is associated with the inhibition of formation, growth and proliferation of the bone mineral hydroxyapatite (HAP). Furthermore, post-translational modifications like phosphorylation can alter conformations and interaction properties of intrinsically disordered proteins (IDPs). Therefore, the actual interaction of OPN with a HAP surface on an atomic level and how this interaction is affected by phosphorylation is of great interest. Here, we study the interaction of full-length OPN on the surface of suspended HAP nanoparticles by solution NMR spectroscopy. We report the binding modes of this IDP and provide evidence for the influence of hyperphosphorylation on the binding character and an explanation for the differing roles in biomineralization. Our study moreover presents an easy and suitable option to measure interaction of nanoparticles in a stable suspension with full-length proteins.
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Affiliation(s)
- Julian Holzinger
- Department of Structural and Computational BiologyUniversity of Vienna, Max Perutz LabsVienna BioCenter Campus 51030ViennaAustria
| | - Harald Kotisch
- Vienna Biocenter Core Facilities GmbHDr. Bohr Gasse 31030ViennaAustria
| | - Klaus W. Richter
- Department of Inorganic Chemistry, Functional MaterialsUniversity of ViennaWähringer Str. 421090ViennaAustria
| | - Robert Konrat
- Department of Structural and Computational BiologyUniversity of Vienna, Max Perutz LabsVienna BioCenter Campus 51030ViennaAustria
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6
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Shaw WJ, Tarasevich BJ, Buchko GW, Arachchige RMJ, Burton SD. Controls of nature: Secondary, tertiary, and quaternary structure of the enamel protein amelogenin in solution and on hydroxyapatite. J Struct Biol 2020; 212:107630. [PMID: 32979496 PMCID: PMC7744360 DOI: 10.1016/j.jsb.2020.107630] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 09/12/2020] [Accepted: 09/17/2020] [Indexed: 10/23/2022]
Abstract
Amelogenin, a protein critical to enamel formation, is presented as a model for understanding how the structure of biomineralization proteins orchestrate biomineral formation. Amelogenin is the predominant biomineralization protein in the early stages of enamel formation and contributes to the controlled formation of hydroxyapatite (HAP) enamel crystals. The resulting enamel mineral is one of the hardest tissues in the human body and one of the hardest biominerals in nature. Structural studies have been hindered by the lack of techniques to evaluate surface adsorbed proteins and by amelogenin's disposition to self-assemble. Recent advancements in solution and solid state nuclear magnetic resonance (NMR) spectroscopy, atomic force microscopy (AFM), and recombinant isotope labeling strategies are now enabling detailed structural studies. These recent studies, coupled with insights from techniques such as CD and IR spectroscopy and computational methodologies, are contributing to important advancements in our structural understanding of amelogenesis. In this review we focus on recent advances in solution and solid state NMR spectroscopy and in situ AFM that reveal new insights into the secondary, tertiary, and quaternary structure of amelogenin by itself and in contact with HAP. These studies have increased our understanding of the interface between amelogenin and HAP and how amelogenin controls enamel formation.
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Affiliation(s)
- Wendy J Shaw
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Barbara J Tarasevich
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Garry W Buchko
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA; School of Molecular Bioscience, Washington State University, Pullman, WA 99164, USA
| | - Rajith M J Arachchige
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Sarah D Burton
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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7
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Chu J, Feng X, Guo H, Zhang T, Zhao H, Zhang Q. Remineralization Efficacy of an Amelogenin-Based Synthetic Peptide on Carious Lesions. Front Physiol 2018; 9:842. [PMID: 30026702 PMCID: PMC6041723 DOI: 10.3389/fphys.2018.00842] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 06/14/2018] [Indexed: 11/13/2022] Open
Abstract
Objective: The aim of this study was to evaluate the remineralization efficacy of an amelogenin-based peptide on initial enamel carious lesions in vitro. Furthermore, we attempted to provide insights into the possible mechanism of the remineralization, including determining the calcium-binding properties of the peptide and its effects on calcium phosphate mineralization. Methods: The peptide comprising the N-terminus and the C-terminus of porcine amelogenin was synthesized by Synpeptide Co., Ltd. Fifty specimens were randomly assigned to five immersing treatment groups for 12 days: remineralizing medium only; 12.5 μg/mL peptide + remineralizing medium; 25 μg/mL peptide + remineralizing medium; 50 μg/mL peptide + remineralizing medium; fluoride + remineralizing medium. After immersion, mean mineral loss before and after remineralization of each specimen was determined using micro-CT. Mean mineral gain after remineralization was calculated. Calcium binding properties were measured by Isothermal titration calorimetry (ITC). TEM and Fourier transform-infrared were used to determine the effects of the peptide on calcium phosphate mineralization. Results: A significant decrease in mineral loss after remineralization process in all groups was observed (p < 0.05). Treatment in remineralizing medium resulted in the lowest mineral gain while the fluoridated treatment exhibited the highest mineral gain among all groups. Inclusion of synthetic peptide in the remineralizing medium exhibited a higher mineral gain and the gain of 50 μg/mL group was greater than that of the 25 μg/mL group. No significant difference in mineral gain was observed between the remineralizing medium only group and the 12.5 μg/mL peptide group (p > 0.05). ITC values showed that the Ca2+-binding affinity of the peptide is about 9.914 × 104M−1. Furthermore, the peptide was found to inhibit calcium phosphate precipitation and stabilize amorphous calcium phosphate formation for more than 2 h and finally transform into ordered hydroxyapatite crystals. Conclusion: Specific concentrations of the amelogenin-based synthetic peptide promoted in vitro remineralization, with higher concentrations exhibiting significantly greater remineralization. This study presented evidence suggesting that the peptide may act as a Ca2+carrier as well as a regulating factor. When the stabilizing calcium and phosphorus ions bind with the peptide they become biologically available for the remineralization of deeper carious lesions, while also regulated by the peptide to transform into ordered hydroxyapatite crystals.
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Affiliation(s)
- Jinpu Chu
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Xiaofang Feng
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Stomatology, Zhengzhou University, Zhengzhou, China
| | - Huijing Guo
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Tieting Zhang
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Hualei Zhao
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Stomatology, Zhengzhou University, Zhengzhou, China
| | - Qun Zhang
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Stomatology, Zhengzhou University, Zhengzhou, China
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8
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Abstract
The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines (ENAMEL) Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National Institute of Dental and Craniofacial Research (NIDCR). Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field.
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9
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Yamazaki H, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Protein Phosphorylation and Mineral Binding Affect the Secondary Structure of the Leucine-Rich Amelogenin Peptide. Front Physiol 2017; 8:450. [PMID: 28706493 PMCID: PMC5489624 DOI: 10.3389/fphys.2017.00450] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 06/14/2017] [Indexed: 12/31/2022] Open
Abstract
Previously, we have shown that serine-16 phosphorylation in native full-length porcine amelogenin (P173) and the Leucine-Rich Amelogenin Peptide (LRAP(+P)), an alternative amelogenin splice product, affects protein assembly and mineralization in vitro. Notably, P173 and LRAP(+P) stabilize amorphous calcium phosphate (ACP) and inhibit hydroxyapatite (HA) formation, while non-phosphorylated counterparts (rP172, LRAP(-P)) guide the growth of ordered bundles of HA crystals. Based on these findings, we hypothesize that the phosphorylation of full-length amelogenin and LRAP induces conformational changes that critically affect its capacity to interact with forming calcium phosphate mineral phases. To test this hypothesis, we have utilized Fourier transform infrared spectroscopy (FTIR) to determine the secondary structure of LRAP(-P) and LRAP(+P) in the absence/presence of calcium and selected mineral phases relevant to amelogenesis; i.e., hydroxyapatite (HA: an enamel crystal prototype) and (ACP: an enamel crystal precursor phase). Aqueous solutions of LRAP(-P) or LRAP(+P) were prepared with or without 7.5 mM of CaCl2 at pH 7.4. FTIR spectra of each solution were obtained using attenuated total reflectance, and amide-I peaks were analyzed to provide secondary structure information. Secondary structures of LRAP(+P) and LRAP(-P) were similarly assessed following incubation with suspensions of HA and pyrophosphate-stabilized ACP. Amide I spectra of LRAP(-P) and LRAP(+P) were found to be distinct from each other in all cases. Spectra analyses showed that LRAP(-P) is comprised mostly of random coil and β-sheet, while LRAP(+P) exhibits more β-sheet and α-helix with little random coil. With added Ca, the random coil content increased in LRAP(-P), while LRAP(+P) exhibited a decrease in α-helix components. Incubation of LRAP(-P) with HA or ACP resulted in comparable increases in β-sheet structure. Notably, however, LRAP(+P) secondary structure was more affected by ACP, primarily showing an increase in β-sheet structure, compared to that observed with added HA. These collective findings indicate that phosphorylation induces unique secondary structural changes that may enhance the functional capacity of native phosphorylated amelogenins like LRAP to stabilize an ACP precursor phase during early stages of enamel mineral formation.
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Affiliation(s)
- Hajime Yamazaki
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, McGowan Institute for Regenerative Medicine, University of PittsburghPittsburgh, PA, United States
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi UniversityYokohama, Japan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, United States
| | - Henry C Margolis
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
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10
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Connelly C, Cicuto T, Leavitt J, Petty A, Litman A, Margolis HC, Gerdon AE. Dynamic interactions of amelogenin with hydroxyapatite surfaces are dependent on protein phosphorylation and solution pH. Colloids Surf B Biointerfaces 2016; 148:377-384. [PMID: 27632699 DOI: 10.1016/j.colsurfb.2016.09.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 08/03/2016] [Accepted: 09/07/2016] [Indexed: 10/21/2022]
Abstract
Amelogenin, the predominant extracellular matrix protein secreted by ameloblasts, has been shown to be essential for proper tooth enamel formation. In this study, amelogenin adsorption to hydroxyapatite (HAP) surfaces, a prototype for enamel mineral, has been studied using a quartz crystal microbalance (QCM) to interrogate effects of protein phosphorylation and solution pH. Dynamic flow-based experiments were conducted at pH 7.4 and 8.0 using native phosphorylated porcine amelogenin (P173) and recombinant non-phosphorylated porcine amelogenin (rP172). Loading capacities (μmol/m2) on HAP surfaces were calculated under all conditions and adsorption affinities (Kad) were calculated when Langmuir isotherm conditions appeared to be met. At pH 8.0, binding characteristics were remarkably similar for the two proteins. However, at pH 7.4 a higher affinity and lower surface loading for the phosphorylated P173 was found compared to any other set of conditions. This suggests that phosphorylated P173 adopts a more extended conformation than non-phosphorylated full-length amelogenin, occupying a larger footprint on the HAP surface. This surface-induced structural difference may help explain why P173 is a more effective inhibitor of spontaneous HAP formation in vitro than rP172. Differences in the viscoelastic properties of P173 and rP172 in the adsorbed state were also observed, consistent with noted differences in HAP binding. These collective findings provide new insight into the important role of amelogenin phosphorylation in the mechanism by which amelogenin regulates enamel crystal formation.
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Affiliation(s)
| | - Thomas Cicuto
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Jason Leavitt
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Alexander Petty
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Amy Litman
- The Forsyth Institute, Center for Biomineralization, Department of Applied Oral Sciences, Cambridge, MA 02142, USA
| | - Henry C Margolis
- The Forsyth Institute, Center for Biomineralization, Department of Applied Oral Sciences, Cambridge, MA 02142, USA
| | - Aren E Gerdon
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA.
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11
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Zhao W, Xu Z, Cui Q, Sahai N. Predicting the Structure-Activity Relationship of Hydroxyapatite-Binding Peptides by Enhanced-Sampling Molecular Simulation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7009-7022. [PMID: 27329793 DOI: 10.1021/acs.langmuir.6b01582] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Understanding the molecular structural and energetic basis of the interactions between peptides and inorganic surfaces is critical to their applications in tissue engineering and biomimetic material synthesis. Despite recent experimental progresses in the identification and functionalization of hydroxyapatite (HAP)-binding peptides, the molecular mechanisms of their interactions with HAP surfaces are yet to be explored. In particular, the traditional method of molecular dynamics (MD) simulation suffers from insufficient sampling at the peptide-inorganic interface that renders the molecular-level observation dubious. Here we demonstrate that an integrated approach combining bioinformatics, MD, and metadynamics provides a powerful tool for investigating the structure-activity relationship of HAP-binding peptides. Four low charge density peptides, previously identified by phage display, have been considered. As revealed by bioinformatics and MD, the binding conformation of the peptides is controlled by both the sequence and the amino acid composition. It was found that formation of hydrogen bonds between lysine residue and phosphate ions on the surface dictates the binding of positively charged peptide to HAP. The binding affinities of the peptides to the surface are estimated by free energy calculation using parallel-tempering metadynamics, and the results compare favorably to measurements reported in previous experimental studies. The calculation suggests that the charge density of the peptide primarily controls the binding affinity to the surface, while the backbone secondary structure that may restrain side chain orientation toward the surface plays a minor role. We also report that the application of enhanced-sampling metadynamics effects a major advantage over the steered MD method by significantly improving the reliability of binding free energy calculation. In general, our novel integration of diverse sampling techniques should contribute to the rational design of surface-recognition peptides in biomedical applications.
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Affiliation(s)
| | | | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison , Madison, Wisconsin 53706-1322, United States
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12
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Lokappa SB, Chandrababu KB, Moradian-Oldak J. Tooth enamel protein amelogenin binds to ameloblast cell membrane-mimicking vesicles via its N-terminus. Biochem Biophys Res Commun 2015; 464:956-61. [PMID: 26188506 PMCID: PMC4532586 DOI: 10.1016/j.bbrc.2015.07.082] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 07/16/2015] [Indexed: 11/18/2022]
Abstract
We have recently reported that the extracellular enamel protein amelogenin has affinity to interact with phospholipids and proposed that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities. Here, in order to identify the liposome-interacting domains of amelogenin we designed four different amelogenin mutants containing only a single tryptophan at positions 25, 45, 112 and 161. Circular dichroism studies of the mutants confirmed that they are structurally similar to the wild-type amelogenin. Utilizing the intrinsic fluorescence of single tryptophan residue and fluorescence resonance energy transfer [FRET], we analyzed the accessibility and strength of their binding with an ameloblast cell membrane-mimicking model membrane (ACML) and a negatively charged liposome used as a membrane model. We found that amelogenin has membrane-binding ability mainly via its N-terminal, close to residues W25 and W45. Significant blue shift was also observed in the fluorescence of a N-terminal peptide following addition of liposomes. We suggest that, among other mechanisms, enamel malformation in cases of Amelogenesis Imperfecta (AI) with mutations at the N-terminal may be the result of defective amelogenin-cell interactions.
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Affiliation(s)
- Sowmya Bekshe Lokappa
- Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Karthik Balakrishna Chandrababu
- Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
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13
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Abstract
Mature tooth enamel is acellular and does not regenerate itself. Developing technologies that rebuild tooth enamel and preserve tooth structure is therefore of great interest. Considering the importance of amelogenin protein in dental enamel formation, its ability to control apatite mineralization in vitro, and its potential to be applied in fabrication of future bio-inspired dental material this review focuses on two major subjects: amelogenin and enamel biomimetics. We review the most recent findings on amelogenin secondary and tertiary structural properties with a focus on its interactions with different targets including other enamel proteins, apatite mineral, and phospholipids. Following a brief overview of enamel hierarchical structure and its mechanical properties we will present the state-of-the-art strategies in the biomimetic reconstruction of human enamel.
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Affiliation(s)
- Qichao Ruan
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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14
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Tarasevich BJ, Philo JS, Maluf NK, Krueger S, Buchko GW, Lin G, Shaw WJ. The leucine-rich amelogenin protein (LRAP) is primarily monomeric and unstructured in physiological solution. J Struct Biol 2015; 190:81-91. [PMID: 25449314 PMCID: PMC4400868 DOI: 10.1016/j.jsb.2014.10.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/17/2014] [Accepted: 10/20/2014] [Indexed: 11/23/2022]
Abstract
Amelogenin proteins are critical to the formation of enamel in teeth and may have roles in controlling growth and regulating microstructures of the intricately woven hydroxyapatite (HAP). Leucine-rich amelogenin protein (LRAP) is a 59-residue splice variant of amelogenin and contains the N- and C-terminal charged regions of the full-length protein thought to control crystal growth. Although the quaternary structure of full-length amelogenin in solution has been well studied and can consist of self-assemblies of monomers called nanospheres, there is limited information on the quaternary structure of LRAP. Here, sedimentation velocity analytical ultracentrifugation (SV) and small angle neutron scattering (SANS) were used to study the tertiary and quaternary structure of LRAP at various pH values, ionic strengths, and concentrations. We found that the monomer is the dominant species of phosphorylated LRAP (LRAP(+P)) over a range of solution conditions (pH 2.7-4.1, pH 4.5-8, 50 mmol/L(mM) to 200 mM NaCl, 0.065-2 mg/mL). The monomer is also the dominant species for unphosphorylated LRAP (LRAP(-P)) at pH 7.4 and for LRAP(+P) in the presence of 2.5 mM calcium at pH 7.4. LRAP aggregates in a narrow pH range near the isoelectric point of pH 4.1. SV and SANS show that the LRAP monomer has a radius of ∼2.0 nm and an asymmetric structure, and solution NMR studies indicate that the monomer is largely unstructured. This work provides new insights into the secondary, tertiary, and quaternary structure of LRAP in solution and provides evidence that the monomeric species may be an important functional form of some amelogenins.
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Affiliation(s)
| | - John S Philo
- Alliance Protein Laboratories, Inc., San Diego, CA 92121, United States
| | - Nasib Karl Maluf
- Alliance Protein Laboratories, Inc., San Diego, CA 92121, United States
| | - Susan Krueger
- National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Garry W Buchko
- Pacific Northwest National Laboratory, Richland, WA 99354, United States
| | - Genyao Lin
- WSP Chemicals & Technology, LLC, Leetsdale, PA 15056, United States
| | - Wendy J Shaw
- Pacific Northwest National Laboratory, Richland, WA 99354, United States
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15
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Lokappa SB, Chandrababu KB, Dutta K, Perovic I, Evans JS, Moradian-Oldak J. Interactions of amelogenin with phospholipids. Biopolymers 2015; 103:96-108. [PMID: 25298002 PMCID: PMC4415992 DOI: 10.1002/bip.22573] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/29/2014] [Accepted: 10/02/2014] [Indexed: 11/08/2022]
Abstract
Amelogenin protein has the potential to interact with other enamel matrix proteins, mineral, and cell surfaces. We investigated the interactions of recombinant amelogenin rP172 with small unilamellar vesicles as model membranes, toward the goal of understanding the mechanisms of amelogenin-cell interactions during amelogenesis. Dynamic light scattering (DLS), fluorescence spectroscopy, circular dichroism (CD), and nuclear magnetic resonance (NMR) were used. In the presence of phospholipid vesicles, a blue shift in the Trp fluorescence emission maxima of rP172 was observed (∼334 nm) and the Trp residues of rP172 were inaccessible to the aqueous quencher acrylamide. DLS studies indicated complexation of rP172 and phospholipids, although the possibility of fusion of phospholipids following amelogenin addition cannot be ruled out. NMR and CD studies revealed a disorder-order transition of rP172 in a model membrane environment. Strong fluorescence resonance energy transfer from Trp in rP172 to DNS-bound-phospholipid was observed, and fluorescence polarization studies indicated that rP172 interacted with the hydrophobic core region of model membranes. Our data suggest that amelogenin has ability to interact with phospholipids and that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities.
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Affiliation(s)
- Sowmya Bekshe Lokappa
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
| | - Karthik Balakrishna Chandrababu
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
| | - Kaushik Dutta
- Laboratory for Chemical Physics, Division of Basic Sciences and Craniofacial Biology, New York University, New York, New York 10010
| | - Iva Perovic
- Laboratory for Chemical Physics, Division of Basic Sciences and Craniofacial Biology, New York University, New York, New York 10010
| | - John Spencer Evans
- Laboratory for Chemical Physics, Division of Basic Sciences and Craniofacial Biology, New York University, New York, New York 10010
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
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16
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Ruan Q, Moradian-Oldak J. Amelogenin and enamel biomimetics. J Mater Chem B 2015. [DOI: 10.1039/c5tb00163c and 21=21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mature tooth enamel is acellular and does not regenerate itself.
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Affiliation(s)
- Qichao Ruan
- Center for Craniofacial Molecular Biology
- Herman Ostrow School of Dentistry
- University of Southern California
- Los Angeles
- USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology
- Herman Ostrow School of Dentistry
- University of Southern California
- Los Angeles
- USA
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17
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Buchko GW, Shaw WJ. Improved protocol to purify untagged amelogenin - Application to murine amelogenin containing the equivalent P70→T point mutation observed in human amelogenesis imperfecta. Protein Expr Purif 2014; 105:14-22. [PMID: 25306873 DOI: 10.1016/j.pep.2014.09.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/17/2014] [Indexed: 11/16/2022]
Abstract
Amelogenin is the predominant extracellular protein responsible for converting carbonated hydroxyapatite into dental enamel, the hardest and most heavily mineralized tissue in vertebrates. Despite much effort, the precise mechanism by which amelogenin regulates enamel formation is not fully understood. To assist efforts aimed at understanding the biochemical mechanism of enamel formation, more facile protocols to purify recombinantly expressed amelogenin, ideally without any tag to assist affinity purification, are advantageous. Here we describe an improved method to purify milligram quantities of amelogenin that exploits its high solubility in 2% glacial acetic acid under conditions of low ionic strength. The method involves heating the frozen cell pellet for two 15min periods at ∼70°C with 2min of sonication in between, dialysis twice in 2% acetic acid (1:250 v/v), and reverse phase chromatography. A further improvement in yield is obtained by resuspending the frozen cell pellet in 6M guanidine hydrochloride in the first step. The acetic acid heating method is illustrated with a murine amelogenin containing the corresponding P70→T point mutation observed in an human amelogenin associated with amelogenesis imperfecta (P71T), while the guanidine hydrochloride heating method is illustrated with wild type murine amelogenin (M180). The self-assembly properties of P71T were probed by NMR chemical shift perturbation studies as a function of protein (0.1-1.8mM) and NaCl (0-367mM) concentration. Relative to similar studies with wild type murine amelogenin, P71T self-associates at lower protein or salt concentrations with the interactions initiated near the N-terminus.
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Affiliation(s)
- Garry W Buchko
- Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Wendy J Shaw
- Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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18
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Lu JX, Burton SD, Xu YS, Buchko GW, Shaw WJ. The flexible structure of the K24S28 region of Leucine-Rich Amelogenin Protein (LRAP) bound to apatites as a function of surface type, calcium, mutation, and ionic strength. Front Physiol 2014; 5:254. [PMID: 25071599 PMCID: PMC4092356 DOI: 10.3389/fphys.2014.00254] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Accepted: 06/17/2014] [Indexed: 12/30/2022] Open
Abstract
Leucine-Rich Amelogenin Protein (LRAP) is a member of the amelogenin family of biomineralization proteins, proteins which play a critical role in enamel formation. Recent studies have revealed the structure and orientation of the N- and C-terminus of LRAP bound to hydroxyapatite (HAP), a surface used as an analog of enamel. The structure of one region, K24 to S28, was found to be sensitive to phosphorylation of S16, the only naturally observed site of serine phosphorylation in LRAP, suggesting that K24S28 may sit at a key region of structural flexibility and play a role in the protein's function. In this work, we investigated the sensitivity of the structure and orientation of this region when bound to HAP as a function of several factors which may vary during enamel formation to influence structure: the ionic strength (0.05, 0.15, 0.2 M), the calcium concentration (0.07 and 0.4 mM), and the surface to which it is binding [HAP and carbonated apatite (CAP), a more direct mimic of enamel]. A naturally occurring mutation found in amelogenin (T21I) was also investigated. The structure in the K24S28 region of the protein was found to be sensitive to these conditions, with the CAP surface and excess Ca(2+) (8:1 [Ca(2+)]:[LRAP-K24S28(+P)]) resulting in a tighter helix, while low ionic strength relaxed the helical structure. Higher ionic strength and the point mutation did not result in any structural change in this region. The distance of the backbone of K24 from the surface was most sensitive to excess Ca(2+) and in the T21I-mutation. Collectively, these data suggest that phosphorylated LRAP is able to accommodate structural changes while maintaining its interaction with the surface, and provides further evidence of the structural sensitivity of the K24S28 region, a sensitivity that may contribute to function in biomineralization.
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Affiliation(s)
| | | | | | | | - Wendy J. Shaw
- Fundamental and Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, USA
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19
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Chandrababu KB, Dutta K, Lokappa SB, Ndao M, Evans JS, Moradian-Oldak J. Structural adaptation of tooth enamel protein amelogenin in the presence of SDS micelles. Biopolymers 2014; 101:525-35. [PMID: 24114119 PMCID: PMC3947416 DOI: 10.1002/bip.22415] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 09/13/2013] [Indexed: 11/10/2022]
Abstract
Amelogenin, the major extracellular matrix protein of developing tooth enamel is intrinsically disordered. Through its interaction with other proteins and mineral, amelogenin assists enamel biomineralization by controlling the formation of highly organized enamel crystal arrays. We used circular dichroism (CD), dynamic light scattering (DLS), fluorescence, and NMR spectroscopy to investigate the folding propensity of recombinant porcine amelogenin rP172 following its interaction with SDS, at levels above critical micelle concentration. The rP172-SDS complex formation was confirmed by DLS, while an increase in the structure moiety of rP172 was noted through CD and fluorescence experiments. Fluorescence quenching analyses performed on several rP172 mutants where all but one Trp was replaced by Tyr at different sequence regions confirmed that the interaction of amelogenin with SDS micelles occurs via the N-terminal region close to Trp25 where helical segments can be detected by NMR. NMR spectroscopy and structural refinement calculations using CS-Rosetta modeling confirm that the highly conserved N-terminal domain is prone to form helical structure when bound to SDS micelles. Our findings reported here reveal interactions leading to significant changes in the secondary structure of rP172 upon treatment with SDS. These interactions may reflect the physiological relevance of the flexible nature of amelogenin and its sequence specific helical propensity that might enable it to structurally adapt with charged and potential targets such as cell surface, mineral, and other proteins during enamel biomineralization.
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Affiliation(s)
- Karthik Balakrishna Chandrababu
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
| | - Kaushik Dutta
- New York Structural Biology Center, 89 Convent Ave, New York, NY 10027
| | - Sowmya Bekshe Lokappa
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
| | - Moise Ndao
- Laboratory for Chemical Physics, Division of Basic Sciences and Craniofacial Biology, New York University, New York, New York 10010
| | - John Spencer Evans
- Laboratory for Chemical Physics, Division of Basic Sciences and Craniofacial Biology, New York University, New York, New York 10010
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033
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20
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Bonhomme C, Gervais C, Laurencin D. Recent NMR developments applied to organic-inorganic materials. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 77:1-48. [PMID: 24411829 DOI: 10.1016/j.pnmrs.2013.10.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/17/2013] [Indexed: 06/03/2023]
Abstract
In this contribution, the latest developments in solid state NMR are presented in the field of organic-inorganic (O/I) materials (or hybrid materials). Such materials involve mineral and organic (including polymeric and biological) components, and can exhibit complex O/I interfaces. Hybrids are currently a major topic of research in nanoscience, and solid state NMR is obviously a pertinent spectroscopic tool of investigation. Its versatility allows the detailed description of the structure and texture of such complex materials. The article is divided in two main parts: in the first one, recent NMR methodological/instrumental developments are presented in connection with hybrid materials. In the second part, an exhaustive overview of the major classes of O/I materials and their NMR characterization is presented.
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Affiliation(s)
- Christian Bonhomme
- Laboratoire de Chimie de la Matière Condensée de Paris, UMR CNRS 7574, Université Pierre et Marie Curie, Paris 06, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.
| | - Christel Gervais
- Laboratoire de Chimie de la Matière Condensée de Paris, UMR CNRS 7574, Université Pierre et Marie Curie, Paris 06, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France
| | - Danielle Laurencin
- Institut Charles Gerhardt de Montpellier, UMR5253, CNRS UM2 UM1 ENSCM, CC1701, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
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21
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Lu JX, Xu YS, Buchko GW, Shaw WJ. Mineral association changes the secondary structure and dynamics of murine amelogenin. J Dent Res 2013; 92:1000-4. [PMID: 24130249 DOI: 10.1177/0022034513504929] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Amelogenin is one of the key protein constituents responsible for the exquisite organization of the calcium phosphate crystals in enamel. Amelogenin forms into nanospheres in solution, while its association with hydroxyapatite is also essential to enamel development. Structural information of full-length amelogenin in either of these physiologically important forms has the potential to provide mechanistic information; however, these data are limited because of the difficulty of determining the structure of large protein complexes and proteins bound to surfaces. To obtain structural insights into amelogenin during these early stages of enamel development, we used a lysine-specific (13)C-, (15)N-labeled sample of murine amelogenin to provide insight into the structure of the hydroxyapatite (HAP)-binding domains of the protein. A combination of one-and two-dimensional solid-state NMR experiments was used to obtain molecular-level insights into the secondary structure and dynamics of full-length amelogenin within a nanosphere-gel and on the surface of HAP. Regions of amelogenin that appear to be primarily random coil in the nanosphere-gel adopt a β-strand structure and are less mobile with HAP binding, indicative of a structural switch upon binding that may be important in the role of amelogenin in enamel development.
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Affiliation(s)
- J X Lu
- Pacific Northwest National Laboratory, Richland, WA 99352, USA
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