Roy Sayantan, Wang Bing, Roy Krittika, Tian Yuan, Bhattacharya Madhurima, Williams Sarah, Yin Qian
Department of Biological Science, Florida State University, Tallahassee, FL, USA.
Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, CT, USA.
Commun Biol. 2025 Feb 22;8(1):282. doi: 10.1038/s42003-025-07727-3.
Guanylate-binding proteins (GBPs) are interferon-inducible GTPases that confer protective immunity against a variety of intracellular pathogens. GBP2 is one of the two highly inducible GBPs, yet the precise mechanisms underlying the activation and regulation of GBP2, in particular the nucleotide-induced conformational changes in GBP2, remain poorly understood. In this study, we elucidate the structural plasticity of GBP2 upon nucleotide binding through crystallographic analysis. By determining the crystal structures of GBP2 G domain (GBP2GD) in complex with GDP and nucleotide-free full-length GBP2 with K51A mutation (GBP2), we unveil distinct conformational states adopted by the nucleotide-binding pocket and distal regions of the protein. Comparison between the nucleotide-free full-length GBP2 structure with homologous structures reveals notable movement in the C-terminal helical region, along with conformational changes in the G domain. Through comparative analysis, we identify subtle but critical differences in the nucleotide-bound states of GBP2, providing insights into the molecular basis of its dimer-monomer transition and enzymatic activity. These findings pave the way for future investigations aimed at elucidating the precise molecular mechanisms underlying GBP2's role in the immune response and open avenues for exploring how the unique functions of GBPs could be leveraged to combat pathogen invasion.
鸟苷酸结合蛋白（GBPs）是干扰素诱导的GTP酶，可赋予针对多种细胞内病原体的保护性免疫。GBP2是两种高度可诱导的GBPs之一，然而，GBP2激活和调控的精确机制，特别是核苷酸诱导的GBP2构象变化，仍知之甚少。在本研究中，我们通过晶体学分析阐明了GBP2在核苷酸结合时的结构可塑性。通过确定与GDP结合的GBP2 G结构域（GBP2GD）以及具有K51A突变的无核苷酸全长GBP2（GBP2）的晶体结构，我们揭示了蛋白质核苷酸结合口袋和远端区域所采用的不同构象状态。无核苷酸全长GBP2结构与同源结构之间的比较揭示了C末端螺旋区域的显著移动，以及G结构域的构象变化。通过比较分析，我们确定了GBP2核苷酸结合状态的细微但关键的差异，为其二聚体-单体转变和酶活性的分子基础提供了见解。这些发现为未来旨在阐明GBP2在免疫反应中作用的精确分子机制的研究铺平了道路，并为探索如何利用GBPs的独特功能对抗病原体入侵开辟了途径。
