Leibniz-Institut Für Molekulare Pharmakologie, Berlin, Germany.
Nat Struct Mol Biol. 2010 Sep;17(9):1037-42. doi: 10.1038/nsmb.1891. Epub 2010 Aug 29.
The small heat shock protein alphaB-crystallin (alphaB) contributes to cellular protection against stress. For decades, high-resolution structural studies on oligomeric alphaB have been confounded by its polydisperse nature. Here, we present a structural basis of oligomer assembly and activation of the chaperone using solid-state NMR and small-angle X-ray scattering (SAXS). The basic building block is a curved dimer, with an angle of approximately 121 degrees between the planes of the beta-sandwich formed by alpha-crystallin domains. The highly conserved IXI motif covers a substrate binding site at pH 7.5. We observe a pH-dependent modulation of the interaction of the IXI motif with beta4 and beta8, consistent with a pH-dependent regulation of the chaperone function. N-terminal region residues Ser59-Trp60-Phe61 are involved in intermolecular interaction with beta3. Intermolecular restraints from NMR and volumetric restraints from SAXS were combined to calculate a model of a 24-subunit alphaB oligomer with tetrahedral symmetry.
小分子热休克蛋白 alphaB-晶状体蛋白（alphaB）有助于细胞抵抗应激。几十年来，对寡聚体 alphaB 的高分辨率结构研究一直受到其多分散性的困扰。在这里，我们使用固态 NMR 和小角 X 射线散射（SAXS）来展示寡聚体组装和伴侣激活的结构基础。基本构建块是一个弯曲的二聚体，由 alpha-晶状体结构域形成的β-三明治平面之间的角度约为 121 度。高度保守的 IXI 基序在 pH7.5 时覆盖了一个底物结合位点。我们观察到 IXI 基序与 beta4 和 beta8 的相互作用存在 pH 依赖性调节，这与伴侣功能的 pH 依赖性调节一致。N 端区域残基 Ser59-Trp60-Phe61 参与与 beta3 的分子间相互作用。来自 NMR 的分子间约束和来自 SAXS 的体积约束被结合起来，以计算具有四面体对称性的 24 个亚基 alphaB 寡聚体的模型。
