Department of Biomineralization, The Forsyth Institute, 245 First Street, Cambridge, MA 02142, USA.
J Dent Res. 2011 Sep;90(9):1091-7. doi: 10.1177/0022034511411301. Epub 2011 Jun 7.
Amelogenin's capacity to regulate enamel formation is related to its conserved N- and C-terminal domains, its ability to self-assemble, and its ability to stabilize amorphous calcium phosphate (ACP) - a capacity enhanced by amelogenin phosphorylation. This in vitro study provides further insight into amelogenin function, using variations of the Leucine-Rich Amelogenin Peptide (LRAP), an alternative splice product comprised solely of amelogenin's N- and C-terminal domains. Peptide self-assembly was studied by dynamic light-scattering and transmission electron microscopy (TEM). TEM, selected area electron diffraction, and Fourier transform-infrared spectroscopy were also used to determine the effect of phosphorylated and non-phosphorylated LRAP on calcium phosphate formation. Results show that phosphorylated and non-phosphorylated LRAP can self-assemble into chain-like structures in a fashion dependent on the C-terminal domain. Notably, this capacity was enhanced by added calcium and to a much greater degree for phosphorylated LRAP. Furthermore, phosphorylated LRAP was found to stabilize ACP and prevent its transformation to hydroxyapatite (HA), while aligned HA crystals formed in the presence of non-phosphorylated LRAP. The N- and C-terminal amelogenin domains in non-phosphorylated LRAP are, therefore, sufficient to guide ACP transformation into ordered bundles of apatite crystals, making LRAP an excellent candidate for biomimetic approaches for enamel regeneration.
釉原蛋白调控釉质形成的能力与其保守的 N 端和 C 端结构域、自组装能力以及稳定无定形磷酸钙 (ACP)的能力有关，而这些能力都可因釉原蛋白磷酸化而增强。本体外研究通过对主要由釉原蛋白 N 端和 C 端结构域组成的剪接变体赖氨酰丰富的釉原蛋白肽 (LRAP)的不同变体的研究，进一步深入了解了釉原蛋白的功能。通过动态光散射和透射电子显微镜 (TEM) 研究了肽的自组装。TEM、选区电子衍射和傅里叶变换红外光谱也用于确定磷酸化和非磷酸化 LRAP 对磷酸钙形成的影响。结果表明，磷酸化和非磷酸化的 LRAP 可以在依赖于 C 端结构域的方式下自组装成链状结构。值得注意的是，这种能力通过添加钙而增强，而磷酸化 LRAP 的增强程度更大。此外，发现磷酸化 LRAP 可以稳定 ACP 并防止其向羟基磷灰石 (HA)转化，而在非磷酸化 LRAP 存在的情况下形成排列整齐的 HA 晶体。因此，非磷酸化 LRAP 中的 N 端和 C 端釉原蛋白结构域足以指导 ACP 向有序的磷灰石晶体束转化，使 LRAP 成为牙釉质再生仿生方法的理想候选物。
