School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
Mol Immunol. 2011 Sep;48(15-16):2144-50. doi: 10.1016/j.molimm.2011.07.014. Epub 2011 Aug 9.
Poxviruses are large DNA viruses that replicate in the cytosol and express numerous proteins to subvert the host immunity. Vaccinia virus A46 is a 25kDa protein that antagonizes multiple components of the Toll-like/interleukin-1 receptor (TLR) pathway by targeting cytosolic adaptor proteins. A46 binds to MyD88, Mal/TIRAP, TRIF and TRAM and suppresses the activation of NF-κB and interferon regulatory factors. Each of these cytosolic adaptors has a TIR domain that is critical for oligomerization during signaling. Although the structure of A46 is unknown, it has alternatively been described as an α/β-fold TIR domain, or an all α-helical Bcl-2 fold. Here we provide experimental evidence that the C-terminus of A46 adopts a dimeric α-helical structure, and that this segment retains the ability to interact with monomeric Mal. Furthermore, a peptide fragment of A46 termed VIPER, previously shown to retain the biological properties of the full-length protein, does not interact with Mal in vitro. In summary, we provide for the first time a biophysical analysis of the binding of a poxvirus protein to a TIR domain-containing adaptor molecule.
痘病毒是在细胞质中复制并表达许多蛋白质来颠覆宿主免疫的大型 DNA 病毒。牛痘病毒 A46 是一种 25kDa 的蛋白质，通过靶向细胞质衔接蛋白拮抗 Toll 样受体/白细胞介素-1 受体 (TLR) 途径的多个成分。A46 与 MyD88、Mal/TIRAP、TRIF 和 TRAM 结合，并抑制 NF-κB 和干扰素调节因子的激活。这些细胞质衔接蛋白中的每一个都具有 TIR 结构域，该结构域对于信号转导过程中的寡聚化至关重要。尽管 A46 的结构未知，但它曾被描述为 α/β 折叠 TIR 结构域，或全 α-螺旋 Bcl-2 折叠。在这里，我们提供了实验证据表明 A46 的 C 末端采用二聚体 α-螺旋结构，并且该片段保留与单体 Mal 相互作用的能力。此外，先前显示保留全长蛋白生物学特性的 A46 的肽片段 VIPER 在体外不与 Mal 相互作用。总之，我们首次提供了痘病毒蛋白与含 TIR 结构域衔接分子结合的生物物理分析。
