Gibson James M, Popham Jennifer M, Raghunathan Vinodhkumar, Stayton Patrick S, Drobny Gary P
Department of Bioengineering, University of Washington, Seattle, Washington 98195, USA.
J Am Chem Soc. 2006 Apr 26;128(16):5364-70. doi: 10.1021/ja056731m.
Extracellular matrix proteins regulate hard tissue growth by acting as adhesion sites for cells, by triggering cell signaling pathways, and by directly regulating the primary and/or secondary crystallization of hydroxyapatite, the mineral component of bone and teeth. Despite the key role that these proteins play in the regulation of hard tissue growth in humans, the exact mechanism used by these proteins to recognize mineral surfaces is poorly understood. Interactions between mineral surfaces and proteins very likely involve specific contacts between the lattice and the protein side chains, so elucidation of the nature of interactions between protein side chains and their corresponding inorganic mineral surfaces will provide insight into the recognition and regulation of hard tissue growth. Isotropic chemical shifts, chemical shift anisotropies (CSAs), NMR line-width information, (13)C rotating frame relaxation measurements, as well as direct detection of correlations between (13)C spins on protein side chains and (31)P spins in the crystal surface with REDOR NMR show that, in the peptide fragment derived from the N-terminal 15 amino acids of salivary statherin (i.e., SN-15), the side chain of the phenylalanine nearest the C-terminus of the peptide (F14) is dynamically constrained and oriented near the surface, whereas the side chain of the phenylalanine located nearest to the peptide's N-terminus (F7) is more mobile and is oriented away from the hydroxyapatite surface. The relative dynamics and proximities of F7 and F14 to the surface together with prior data obtained for the side chain of SN-15's unique lysine (i.e., K6) were used to construct a new picture for the structure of the surface-bound peptide and its orientation to the crystal surface.
细胞外基质蛋白通过充当细胞的黏附位点、触发细胞信号通路以及直接调节羟基磷灰石（骨骼和牙齿的矿物质成分）的一次和/或二次结晶来调节硬组织生长。尽管这些蛋白在人类硬组织生长调节中发挥着关键作用，但它们识别矿物质表面的确切机制仍知之甚少。矿物质表面与蛋白之间的相互作用很可能涉及晶格与蛋白侧链之间的特定接触，因此阐明蛋白侧链与其相应无机矿物质表面之间相互作用的本质，将有助于深入了解硬组织生长的识别和调节。各向同性化学位移、化学位移各向异性（CSA）、核磁共振线宽信息、（13）C旋转坐标系弛豫测量，以及利用REDOR核磁共振直接检测蛋白侧链上的（13）C自旋与晶体表面上的（31）P自旋之间的相关性，结果表明，在源自唾液富组蛋白N端15个氨基酸的肽片段（即SN - 15）中，最靠近肽C端的苯丙氨酸（F14）的侧链在表面附近受到动态约束并定向，而最靠近肽N端的苯丙氨酸（F7）的侧链更具流动性且远离羟基磷灰石表面定向。F7和F14与表面的相对动力学和接近程度，以及先前针对SN - 15独特赖氨酸（即K6）侧链获得的数据，被用于构建表面结合肽的结构及其与晶体表面取向的新图景。
