Kohno T, Kobayashi K, Maeda T, Sato K, Takashima A
Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Biochemistry. 1996 Dec 17;35(50):16094-104. doi: 10.1021/bi961598j.
The three-dimensional structure of amyloid beta peptide (25-35), which has neurotoxic activity, in lithium dodecyl sulfate micelles was determined by two-dimensional 1H NMR spectroscopy with simulated annealing calculations. A total of 20 converged amyloid beta peptide structures were obtained on the basis of 110 experimental constraints, including 106 distance constraints reduced from the nuclear Overhauser effect (NOE) connectivities and four torsion angle (phi) constraints. The atomic root mean square difference about averaged coordinates is 1.04 +/- 0.25 A for the backbone atoms (N, C alpha, C) and 1.39 +/- 0.27 A for all heavy atoms of the entire peptide. The molecular structure of amyloid beta peptide in membrane-mimicking environment is composed of a short alpha helix in the C terminal position. The three residues from the N-terminus are disordered, but the remaining eight C-terminal residues are well-ordered, which is supported by the RMSD values of the C-terminal region, Lys28-Leu34. In this region, the RMS differences from averaged coordinates are 0.26 +/- 0.11 A for the backbone atoms (N, C alpha, C) and 0.77 +/- 0.21 A for all heavy atoms, which is very low compared with those for the entire peptide. The four amino acid residues from the N-terminus are hydrophilic and the other seven amino acid residues in C-terminus are hydrophobic. So, our results show that the C-terminal region of amyloid beta peptide (25-35) is buried in the membrane and assumes alpha-helical structure, whereas the N-terminal region is exposed to the solvent with a flexible structure. This structure is very similar to membrane-mediated structure of substance P previously reported. The three-dimensional structure of a non-neurotoxic mutant of amyloid beta peptide (25-35), where Asn27 is replaced by Ala, in lithium dodecyl sulfate micelles was also determined. The structure is similar to that of the wild type amyloid beta peptide (25-35) in the C-terminal region, but the N-terminal flexible region is different. The structural comparison of amyloid beta peptide (25-35), its non-neurotoxic mutant and substance P gives a structural basis to understand the mechanism of neurotoxicity caused by amyloid beta peptide.
通过二维¹H NMR光谱结合模拟退火计算，确定了具有神经毒性活性的淀粉样β肽（25 - 35）在十二烷基硫酸锂胶束中的三维结构。基于110个实验约束条件，共获得了20个收敛的淀粉样β肽结构，其中包括从核Overhauser效应（NOE）连接性推导得到的106个距离约束以及4个扭转角（phi）约束。整个肽段主链原子（N、Cα、C）相对于平均坐标的原子均方根偏差为1.04±0.25 Å，所有重原子的均方根偏差为1.39±0.27 Å。在模拟膜环境中，淀粉样β肽的分子结构由C端位置的一个短α螺旋组成。N端的三个残基无序，但其余八个C端残基有序，这一点由C端区域（Lys28 - Leu34）的均方根偏差值得到支持。在该区域，主链原子（N、Cα、C）相对于平均坐标的均方根偏差为0.26±0.11 Å，所有重原子的均方根偏差为0.77±0.21 Å，与整个肽段相比非常低。N端的四个氨基酸残基亲水，C端的其他七个氨基酸残基疏水。因此，我们的结果表明，淀粉样β肽（25 - 35）的C端区域埋于膜中并呈现α螺旋结构，而N端区域以灵活的结构暴露于溶剂中。这种结构与先前报道的P物质的膜介导结构非常相似。还确定了淀粉样β肽（25 - 35）的非神经毒性突变体（其中Asn27被Ala取代）在十二烷基硫酸锂胶束中的三维结构。该结构在C端区域与野生型淀粉样β肽（25 - 35）相似，但N端的灵活区域不同。淀粉样β肽（25 - 35）、其非神经毒性突变体和P物质的结构比较为理解淀粉样β肽引起神经毒性的机制提供了结构基础。
