Tyrosine Residues Mediate Fibril Formation in a Dynamic Light Chain Dimer Interface
Tyrosine Residues Mediate Fibril Formation in a Dynamic Light Chain Dimer Interface
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DOI：
10.1074/jbc.m112.362921
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发表时间：
2012-08-10
影响因子：
4.8
通讯作者：
Ramirez-Alvarado, Marina
中科院分区：
文献类型：
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作者：
DiCostanzo, Ara Celi;Thompson, James R.;Ramirez-Alvarado, Marina
轻链淀粉样变性是一种无法治愈的蛋白质错误折叠疾病，其中单克隆免疫球蛋白轻链错误折叠并存款为淀粉样纤维，导致器官衰竭和死亡。先前，我们确定淀粉样蛋白生成轻链AL-09和AL-103在pH 10下不形成原纤维（酪氨酸pK（a））。有三个酪氨酸残基（32，91和96）聚集在二聚体界面，不同的相互作用，在两个轻链蛋白质，由于其两个不同的二聚体构象。这些酪氨酸可以在pH 10下离子化，引起排斥并抑制原纤维形成。在这里，我们表征了AL-09和AL-103中的单和双Tyr至Phe突变。所有AL-09 Tyr-至-Phe突变体在pH 10下形成原纤维，而AL-103突变体在pH 10下均不形成原纤维。NMR研究表明，虽然AL-09和AL-103都存在构象异质性，但只有AL-09有利于二聚体构象，其中酪氨酸残基介导淀粉样蛋白形成的关键相互作用。
Light chain amyloidosis is an incurable protein misfolding disease where monoclonal immunoglobulin light chains misfold and deposit as amyloid fibrils, causing organ failure and death. Previously, we determined that amyloidogenic light chains AL-09 and AL-103 do not form fibrils at pH 10 (tyrosine pK(a)). There are three tyrosine residues (32, 91, and 96) clustered in the dimer interface, interacting differently in the two light chain proteins due to their two different dimer conformations. These tyrosines may be ionized at pH 10, causing repulsion and inhibiting fibril formation. Here, we characterize single and double Tyr-to-Phe mutations in AL-09 and AL-103. All AL-09 Tyr-to-Phe mutants form fibrils at pH 10, whereas none of the AL-103 mutants form fibrils at pH 10. NMR studies suggest that although both AL-09 and AL-103 present conformational heterogeneity, only AL-09 favors dimer conformations where tyrosine residues mediate crucial interactions for amyloid formation.