The three-dimensional structure of bovine calcium ion-bound osteocalcin using HNMR spectroscopy
The three-dimensional structure of bovine calcium ion-bound osteocalcin using HNMR spectroscopy
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DOI：
10.1021/bi034470s
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发表时间：
2003-07-01
期刊：
影响因子：
2.9
通讯作者：
Gundberg, CM
中科院分区：
文献类型：
--
作者：
Dowd, TL;Rosen, JF;Gundberg, CM
关于骨钙素或其他非胶原性骨蛋白的结构信息非常有限。我们已经解决了三维结构的钙结合骨钙素使用H-1二维核磁共振技术，并提出了一种机制，矿物结合。使用标准二维同源NMR实验指定49个氨基酸序列中的质子。距离约束，二面角约束，氢键，H-1和C-13化学位移都被用来计算一个家庭的13个结构。蛋白质的三级结构由非结构化的N末端和通过长程疏水相互作用形成的C末端环（残基16-49）组成。残基16-49内的二级结构元件包括III型转角（残基20-25）和两个α-螺旋区（残基27 - 35和41-44）。三个Gla残基从螺旋圈的同一面突出，并且是表面暴露的。采用遗传算法-分子动力学模拟方法，将三个钙原子置于NMR衍生结构上。一个钙原子由三个侧链氧原子配位，两个来自Asp 30，一个来自Gla 24。第二个钙原子与四个氧原子配位，两个来自Gla 24的侧链，两个来自Gla 21的侧链。第三个钙原子与Gla 17侧链的两个氧原子配位。未配位的Gla氧原子之间的距离的最佳相关性与羟基磷灰石中9.43埃的钙间距有关。该结构可以提供进一步了解骨钙素的功能。
Structural information on osteocalcin or other noncollagenous bone proteins is very limited. We have solved the three-dimensional structure of calcium bound osteocalcin using H-1 2D NMR techniques and proposed a mechanism for mineral binding. The protons in the 49 amino acid sequence were assigned using standard two-dimensional homonuclear NMR experiments. Distance constraints, dihedral angle constraints, hydrogen bonds, and H-1 and C-13 chemical shifts were all used to calculate a family of 13 structures. The tertiary structure of the protein consisted of an unstructured N terminus and a C-terminal loop (residues 16-49) formed by long-range hydrophobic interactions. Elements of secondary structure within residues 16-49 include type III turns (residues 20-25) and two (x-helical regions (residues 2735 and 41-44). The three Gla residues project from the same face of the helical turns and are surface exposed. The genetic algorithm-molecular dynamics simulation approach was used to place three calcium atoms on the NMR-derived structure. One calcium atom was coordinated by three side chain oxygen atoms, two from Asp30, and one from Gla24. The second calcium atom was coordinated to four oxygen atoms, two from the side chain in Gla 24, and two from the side chain of Gla 21. The third calcium atom was coordinated to two oxygen atoms of the side chain of Gla17. The best correlation of the distances between the uncoordinated Gla oxygen atoms is with the intercalcium distance of 9.43 Angstrom in hydroxyapatite. The structure may provide further insight into the function of osteocalcin.