Fujisawa R, Kuboki Y
Department of Biochemistry, School of Dentistry, Hokkaido University, Sapporo, Japan.
Eur J Oral Sci. 1998 Jan;106 Suppl 1:249-53. doi: 10.1111/j.1600-0722.1998.tb02183.x.
Phosphophoryn, the major noncollagenous protein of dentin, was adsorbed on synthetic hydroxyapatite crystals and analyzed by high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. Binding of the protein was inhibited by acidic polypeptides, especially by a phosphorylated peptide. After phosphophoryn was incubated with the crystals, the crystals were collected and analyzed by 13C-cross-polarization magic-angle-spinning NMR. Several signals could be assigned to carbons of aspartic acids, taking advantage of the unique amino acid composition of this protein. Chemical shifts of signals of aspartic acids are known to reflect secondary structure of the polypeptide. The chemical shifts obtained from the phosphophoryn indicate that the secondary structure of this protein on the crystal was near to a beta-sheet structure. This result is consistent with the result for poly(Asp) adsorbed on the crystals. The beta-sheet-like structure enables phosphophoryn to extend on the crystal surface and to cover the surface with only a small number of the molecules, resulting in the high inhibitory effect of this protein on crystal growth.
磷蛋白是牙本质的主要非胶原蛋白，它吸附在合成羟基磷灰石晶体上，并通过高分辨率固态核磁共振（NMR）光谱进行分析。该蛋白的结合受到酸性多肽的抑制，尤其是磷酸化肽。磷蛋白与晶体孵育后，收集晶体并通过13C交叉极化魔角旋转NMR进行分析。利用该蛋白独特的氨基酸组成，几个信号可归属于天冬氨酸的碳。已知天冬氨酸信号的化学位移反映多肽的二级结构。从磷蛋白获得的化学位移表明，该蛋白在晶体上的二级结构接近β-折叠结构。这一结果与吸附在晶体上的聚天冬氨酸的结果一致。β-折叠样结构使磷蛋白能够在晶体表面伸展，并且只需少量分子就能覆盖表面，从而导致该蛋白对晶体生长具有高度抑制作用。
