HELIX-TURN-HELIX PEPTIDES THAT FORM A-HELICAL FIBRILS

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。高密度脂蛋白（HDL）大小的主要决定因素是其主要蛋白质载脂蛋白A-I（apo A-I）。载脂蛋白A-I的模型预测，它包含10个两亲性α-螺旋段连接的转折。我们合成了具有两个18-残基的两亲性α-螺旋片段的四种肽（Anantharamaiah，G. M.例如，（1985）J.Biol.Chem.260，10248-10255），其由来自apo A-I的推定转角序列连接。 1. Ac-DWLKAFYDKVAEKLKEAFKVEPLRADWLKAFYDKVAEKLKEAF-NH2 Ac-DWLKAFYDKVAEKLKEAFGLLPVLEDWLKAFYDKVAEKLKEAF-NH2 3. Ac-DWLKAFYDKVAEKLKEAFKVQPYLDDWLKAFYDKVAEKLKEAF-NH2 4. Ac-DWLKAFYDKVAEKLKEAFNGGARLADWLKAFYDKVAEKLKEAF-NH 2肽1-4在37 ° C下在10 mM磷酸钠（pH 7.60）中孵育后形成沉淀。然而，与典型的β折叠淀粉样蛋白原纤维的预期相反，肽1和2形成的原纤维不结合硫磺素T，并诱导刚果红光谱的蓝移。来自肽1和2的原纤维的圆二色性（CD）和傅立叶变换红外光谱（FTIR）显示出显著的α-螺旋特征。同步加速器X射线纤维衍射的磁性排列的样品1已证实的α-螺旋特性的原纤维。这些数据表明由肽1-4形成的沉淀物或原纤维在结构上是多样的。肽1和肽2形成了吗？螺旋形原纤维，螺旋轴垂直于主原纤维轴。与1和2相反，在37 ℃下孵育3和4 30天后仅观察到少量沉淀，并且这些是通过硫磺素T和刚果红结合的典型淀粉样纤维。这些研究表明，较长的两亲性α-螺旋片段之间不同的转角序列可以调节原纤维的结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A major determinant of High Density Lipoprotein (HDL) size is its main protein, Apolipoprotein A-I (apo A-I). Models of apo A-I predict that it contains 10 amphiphilic alpha-helical segments connected by turns. We synthesized four peptides with two 18-residue, amphiphilic alpha-helical segments (Anantharamaiah, G. M. et al., (1985) J. Biol. Chem. 260, 10248-10255) connected by putative turn sequences from apo A-I. 1. Ac-DWLKAFYDKVAEKLKEAFKVEPLRADWLKAFYDKVAEKLKEAF-NH2 2. Ac-DWLKAFYDKVAEKLKEAFGLLPVLEDWLKAFYDKVAEKLKEAF-NH2 3. Ac-DWLKAFYDKVAEKLKEAFKVQPYLDDWLKAFYDKVAEKLKEAF-NH2 4. Ac-DWLKAFYDKVAEKLKEAFNGGARLADWLKAFYDKVAEKLKEAF-NH2 Peptides 1-4 formed precipitates after incubating them at 37¿C in 10 mM sodium phosphate, pH 7.60. In contrast to what is expected for typical beta-sheet amyloid fibrils, however, peptides 1 and 2 formed fibrils that did not bind thioflavin T and induced a blue shift in the spectrum of Congo red. Circular dichroism (CD) and Fourier Transform Infrared Spectroscopy (FTIR) of the fibrils from peptides 1 and 2 show significant alpha-helical character. Synchrotron x-ray fiber diffraction on a magnetically aligned sample of 1 has confirmed the alpha-helical character in the fibrils. These data indicate that precipitates or fibrils formed from peptides 1-4 are structurally diverse. Peptides 1 and 2 formed ?-helical fibrils, with helical axes perpendicular to the main fibril axis. In contrast to 1 and 2, only a small amount of precipitate was observed after incubating 3 and 4 at 37¿C for 30 days, and these are typical amyloid fibrils by thioflavin T and Congo red binding. These studies indicate that varying turn sequences between longer amphiphilic alpha-helical segments can modulate the structure of fibrils.