A pH-Dependent Dimer Lock in Spider Silk Protein
A pH-Dependent Dimer Lock in Spider Silk Protein
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DOI：
10.1016/j.jmb.2010.09.054
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发表时间：
2010-11-26
影响因子：
5.6
通讯作者：
Bergman, Tomas
中科院分区：
文献类型：
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作者：
Landreh, Michael;Askarieh, Glareh;Bergman, Tomas
蜘蛛牵引丝是自然界中最强的聚合物之一，由被称为主要壶腹蜘蛛蛋白(MASP)1和MaSp2的蛋白质组成。由南方真蜘蛛产生的MaSp1的N-末端(NT)结构域起着pH敏感的继电器的作用，在pH 6.3左右介导蜘蛛素的组装。利用酰胺氢/氚交换结合质谱仪(MS)，我们检测到依赖于pH的氘掺入NT结构域核心的变化，表明在低pH下整体结构稳定。在高离子强度或表面暴露的残基Asp40和Glu84与相应的酰胺交换时，稳定作用减弱或消失。非变性电喷雾电离质谱仪显示，当pH值低于但不高于-6.4时，气相中存在二聚体，表明在低pH时依赖于Asp40和Glu84的紧密静电缔合。分析超速离心法的结果支持这些发现。总而言之，这些数据表明了一种将PH值降低到
Spider dragline silk, one of the strongest polymers in nature, is composed of proteins termed major ampullate spidroin (MaSp) 1 and MaSp2. The N-terminal (NT) domain of MaSp1 produced by the nursery web spider Euprosthenops australis acts as a pH-sensitive relay, mediating spidroin assembly at around pH 6.3. Using amide hydrogen/deuterium exchange combined with mass spectrometry (MS), we detected pH-dependent changes in deuterium incorporation into the core of the NT domain, indicating global structural stabilization at low pH. The stabilizing effects were diminished or abolished at high ionic strength, or when the surface-exposed residues Asp40 and Glu84 had been exchanged with the corresponding amides. Nondenaturing electrospray ionization MS revealed the presence of dimers in the gas phase at pH values below-but not above-6.4, indicating a tight electrostatic association that is dependent on Asp40 and Glu84 at low pH. Results from analytical ultracentrifugation support these findings. Together, the data suggest a mechanism whereby lowering the pH to