Structural basis for GTP-induced dimerization and antiviral function of guanylate-binding proteins
Structural basis for GTP-induced dimerization and antiviral function of guanylate-binding proteins
复制标题
GTP 诱导的鸟苷酸结合蛋白二聚化和抗病毒功能的结构基础
DOI：
10.1073/pnas.2022269118
复制
发表时间：
2021-04-13
影响因子：
11.1
通讯作者：
Yang，Haitao
中科院分区：
文献类型：
--
作者：
Cui，Wen;Braun，Elisabeth;Yang，Haitao
意义 鸟苷酸结合蛋白 (GBP) 属于干扰素诱导型 GTP 酶，可介导针对各种病原体的广谱先天免疫反应。它们的保护功能需要通过核苷酸结合和/或催化诱导寡聚化，但实际的分子机制仍然难以捉摸。在这里，我们报告了人 GBP5 (hGBP5) 在无核苷酸状态和核苷酸结合状态下的晶体结构，以及无核苷酸人 GBP2 (hGBP2) 的晶体结构。我们发现 hGBP5 在 GTP 加载后形成封闭的面对面二聚体。这种闭合构象对其抗 HIV-1 活性至关重要。此外，通过 hGBP2 结构和 SAXS 验证，我们提出了 GTP 诱导的 GBP 组装的合理工作模型。我们的研究结果为更好地理解 GBP 的分子机制及其免疫功能奠定了基础。鸟苷酸结合蛋白 (GBP) 形成了一个与动力相关的大型 GTP 酶家族，可介导重要的先天免疫功能。有人建议它们在 GTP 结合/水解时形成寡聚物，但分子机制仍然难以捉摸。在这里，我们展示了 C 端截短的人 GBP5 (hGBP51-486) 的晶体结构，包括大 GTP 酶 (LG) 和中 (MD) 结构域，处于无核苷酸单体和核苷酸结合二聚体状态，以及无核苷酸全长人 GBP2。 GTP 加载后，hGBP51-486 形成封闭的面对面二聚体。 hGBP5 的 MD 相对于其 LG 结构域发生剧烈运动，并与配对分子的 LG 结构域和 MD 形成广泛的相互作用。破坏 MD 界面（对于 hGBP5）或突变铰链区（对于 hGBP2/5）会削弱它们抑制 HIV-1 的能力。我们的结果指出，GTP 诱导的二聚化模式可能在所有 GBP 成员中保守，并提供了对其抗病毒功能的分子决定因素的见解。
Significance Guanylate-binding proteins (GBPs) belong to interferon-inducible GTPases and mediate a broad spectrum of innate immune responses against various pathogens. Their protective functions require oligomerization induced by nucleotide binding and/or catalysis, but the actual molecular mechanisms are still elusive. Here, we report the crystal structures of human GBP5 (hGBP5) in both its nucleotide-free state and nucleotide-bound state, as well as nucleotide-free human GBP2 (hGBP2). We show that hGBP5 forms a closed face-to-face dimer upon GTP loading. This closed conformation is crucial to its anti–HIV-1 activity. Furthermore, with hGBP2 structure and SAXS validation, we propose a plausible working model for GTP-induced assembly of GBPs. Our findings lay the foundation to better understand the molecular mechanisms of GBPs and their immune functions. Guanylate-binding proteins (GBPs) form a family of dynamin-related large GTPases which mediate important innate immune functions. They were proposed to form oligomers upon GTP binding/hydrolysis, but the molecular mechanisms remain elusive. Here, we present crystal structures of C-terminally truncated human GBP5 (hGBP51–486), comprising the large GTPase (LG) and middle (MD) domains, in both its nucleotide-free monomeric and nucleotide-bound dimeric states, together with nucleotide-free full-length human GBP2. Upon GTP-loading, hGBP51–486 forms a closed face-to-face dimer. The MD of hGBP5 undergoes a drastic movement relative to its LG domain and forms extensive interactions with the LG domain and MD of the pairing molecule. Disrupting the MD interface (for hGBP5) or mutating the hinge region (for hGBP2/5) impairs their ability to inhibit HIV-1. Our results point to a GTP-induced dimerization mode that is likely conserved among all GBP members and provide insights into the molecular determinants of their antiviral function.