Enamel biomineralization: Solution- and solid-state NMR
EMSL Project ID
41891
Abstract
Dental enamel, the layer of elongated carbonated hydroxyapatite on the outer layer of the tooth, is the hardest tissue in the human body. It needs to be strong because it cannot repair itself nor can it undergo remodeling, and consequently, it must last a lifetime of exposure to repeated masticatory, parafunctional, and occasional impact loading. Enamel's strength arises from its unique three-dimensional structural organization consisting of unusually long hydroxyapatite (HAP) crystals, over 1000 times longer than the HAP crystals found in bone. The proteins present during enamel development control the formation of this exquisite structure in a series of precisely timed steps, and amelogenins constitute >90% of this protein. Molecular biology techniques have provided significant insight into amelogenin's possible role in all aspects of crystal regulation, including nucleation, growth, inhibition and spacing. However, none of these roles are clearly understood on a molecular level. Experimental evidence in vivo and in vitro shows that amelogenin monomers self-assemble to form nanospheres and that this structure is required to regulate the crystal habit. The environment of the enamel fluid fluctuates during enamel development and these changes (pH, ionic strength and protein concentration) alter the size and distribution of the nanosphere in the process of enamel formation. Naturally occurring mutant amelogenins containing single amino acid alterations (T21 to I or P41 to T) result in nanospheres with a much broader size distribution in vitro, and the consequences are malformed enamel. Clearly, the macroscopic observation that nanosphere size distribution is directly related to proper enamel formation suggests that there are precise molecular level interactions, controlled by secondary and tertiary structure, defining the protein-protein interactions within the nanosphere and its interaction with HAP crystals. How the different quaternary structures work together to form proper enamel is not understood, and consequently, how point mutations result in malformed enamel is also not understood. The principal goal of our research is to determine the molecular structure and interfacial interactions of amelogenin during all of the stages of enamel formation, and consequently, the mechanisms used by amelogenins to regulate biomineralization processes in the extracellular environment. This knowledge will be applied to understanding the mechanisms that govern altered mineral regulation in mutated amelogenins. To attain these goals access to many of the resources present at the Environmental Molecular Sciences Laboratory (EMSL) are required.
Project Details
Project type
Exploratory Research
Start Date
2010-11-24
End Date
2011-11-27
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Buchko GW, G Lin, BJ Tarasevich, and WJ Shaw. 2013. "A solution NMR investigation into the impaired self-assembly properties of two murine amelogenins containing the point mutations T21?I or P41?T." Archives of Biochemistry and Biophysics 537(2):217-224. doi:10.1016/j.abb.2013.07.015
G.W. Buchko and W.J. Shaw (2015) Improved protocol to purify untagged amelogenin - Application to murine amelogenin containing the equivalent P70&8594T point mutation observed in human amelogenesis imperfecta. Protein Expr. Purif.. 105:14-22.
Lu J, Y Xu, GW Buchko, and WJ Shaw. 2013. "Mineral Association Changes the Secondary Structure and Dynamics of Murine Amelogenin." Journal of Dental Research 92(11):1000-1004. doi:10.1177/0022034513504929
Tao J, GW Buchko, WJ Shaw, J De Yoreo, and BJ Tarasevich. 2015. "Sequence-defined Energetic Shifts Control the Disassembly Kinetics and Microstructure of Amelogenin Adsorbed onto Hydroxyapatite (100)." Langmuir 31(38):10451-10460. doi:10.1021/acs.langmuir.5b02549