Highly populated turn conformations in natively unfolded Tau protein identified from residual dipolar couplings and molecular simulation
Highly populated turn conformations in natively unfolded Tau protein identified from residual dipolar couplings and molecular simulation
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DOI：
10.1021/ja0690159
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发表时间：
2007-04-25
影响因子：
15
通讯作者：
Blackledge, Martin
中科院分区：
文献类型：
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作者：
Mukrasch, Marco D.;Markwick, Phineus;Blackledge, Martin
Tau是一种天然的非结构蛋白，调节神经元微管的组织，在阿尔茨海默病和其他神经退行性疾病的神经纤维缠结中也发现了高浓度的tau。这些截然不同的健康和病理形式之间的构象转换仍然知之甚少。我们已经测量了tau的K18结构中的残余偶极耦合(RDC)、J偶联和核Overhauser增强(NOE)，包含所有四个重复结构域R1-R4。NHN RDC与基于描述溶液中未折叠蛋白质的内在构象采样的统计模型的预测进行了比较。虽然RDC的局部变异和相对幅度与大多数蛋白质的倾向性预测一致，但每个重复结构域(重复序列R1-R4中的DLKN、DLSN、DLSK和DKFD)的同源序列显示出强烈的不一致，其特征是中心偶联的符号倒置。显性溶剂中的加速分子动力学模拟(AMD)显示出强烈的转弯倾向，被鉴定为重复序列R1-R3的I型贝塔转弯。将AMD产生的主干二面体采样合并到统计线圈模型中，可以很好地再现RDC实验值。这些局部化的序列依赖的构象倾向打破了在相邻链中采样更多延伸构象的倾向，并对局部环境因素具有显著的抵抗力，这从RDC特征即使在严酷的变性条件下(8M尿素)也能持久存在就证明了这一点。讨论了这种特殊的构象行为在向病理形式的转变中可能起到的作用。
Tau, a natively unstructured protein that regulates the organization of neuronal microtubules, is also found in high concentrations in neurofibrillary tangles of Alzheimer's disease and other neurodegenerative disorders. The conformational transition between these vastly different healthy and pathological forms remains poorly understood. We have measured residual dipolar couplings (RDCs), J-couplings, and nuclear Overhauser enhancement (NOE) in construct K18 of tau, containing all four repeat domains R1-R4. NHN RDCs were compared with prediction on the basis of a statistical model describing the intrinsic conformational sampling of unfolded proteins in solution. While local variation and relative amplitude of RDCs agrees with propensity-based prediction for most of the protein, homologous sequences in each repeat domain (DLKN, DLSN, DLSK, and DKFD in repeats R1-R4) show strong disagreement characterized by inversion of the sign of the central couplings. Accelerated molecular dynamic simulations (AMD) in explicit solvent revealed strong tendencies to form turns, identified as type I beta-turns for repeats R1-R3. Incorporation of the backbone dihedral sampling resulting from AMD into the statistical coil model closely reproduces experimental RDC values. These localized sequence-dependent conformational tendencies interrupt the propensity to sample more extended conformations in adjacent strands and are remarkably resistant to local environmental factors, as demonstrated by the persistence of the RDC signature even under harsh denaturing conditions (8 M urea). The role that this specific conformational behavior may play in the transition to the pathological form is discussed.