Eukaryotic TIR (Toll/interleukin-1 receptor protein) domains signal via TIR-TIR interactions, either by self-association or by interaction with other TIR domains. In mammals, TIR domains are found in Toll-like receptors (TLRs) and cytoplasmic adaptor proteins involved in pro-inflammatory signaling. Previous work revealed that the MAL TIR domain (MALTIR) nucleates the assembly of MyD88TIR into crystalline arrays in vitro. A microcrystal electron diffraction (MicroED) structure of the MyD88TIR assembly has previously been solved, revealing a two-stranded higher-order assembly of TIR domains. In this work, it is demonstrated that the TIR domain of TLR2, which is reported to signal as a heterodimer with either TLR1 or TLR6, induces the formation of crystalline higher-order assemblies of MyD88TIR in vitro, whereas TLR1TIR and TLR6TIR do not. Using an improved data-collection protocol, the MicroED structure of TLR2TIR-induced MyD88TIR microcrystals was determined at a higher resolution (2.85 Å) and with higher completeness (89%) compared with the previous structure of the MALTIR-induced MyD88TIR assembly. Both assemblies exhibit conformational differences in several areas that are important for signaling (for example the BB loop and CD loop) compared with their monomeric structures. These data suggest that TLR2TIR and MALTIR interact with MyD88 in an analogous manner during signaling, nucleating MyD88TIR assemblies unidirectionally.

中文翻译：

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Toll 样受体 2 TIR 结构域成核 MyD88 TIR 结构域高阶组装的微晶电子衍射结构。


真核生物 TIR（Toll/白细胞介素-1 受体蛋白）结构域通过 TIR-TIR 相互作用发出信号，通过自缔合或与其他 TIR 结构域相互作用。在哺乳动物中，TIR 结构域存在于 Toll 样受体 （TLR） 和参与促炎信号传导的细胞质衔接蛋白中。以前的工作揭示了 MAL TIR 结构域 （MALTIR） 在体外将 MyD88TIR 组装成核成核阵列。MyD88TIR 组装体的微晶电子衍射 （MicroED） 结构先前已被解析，揭示了 TIR 域的两链高阶组装。在这项工作中，证明 TLR2 的 TIR 结构域（据报道与 TLR1 或 TLR6 一起作为异二聚体发出信号）在体外诱导 MyD88TIR 结晶高阶组装体的形成，而 TLR1TIR 和 TLR6TIR 则不会。使用改进的数据收集方案，与 MALTIR 诱导的 MyD88TIR 组装的先前结构相比，以更高的分辨率 （2.85 Å） 和更高的完整性 （89%） 确定了 TLR2TIR 诱导的 MyD88TIR 微晶的 MicroED 结构。与它们的单体结构相比，这两个组装体在对信号转导很重要的几个区域（例如 BB 环和 CD 环）表现出构象差异。这些数据表明，TLR2TIR 和 MALTIR 在信号转导过程中以类似的方式与 MyD88 相互作用，使 MyD88TIR 组装体单向成核。