Biochemistry Department, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
Dev Cell. 2013 May 28;25(4):364-73. doi: 10.1016/j.devcel.2013.04.003. Epub 2013 May 9.
ALIX plays a role in nucleocapsid release during viral infection, as does lysobisphosphatidic acid (LBPA). However, the mechanism remains unclear. Here we report that LBPA is recognized within an exposed site in ALIX Bro1 domain predicted by MODA, an algorithm for discovering membrane-docking areas in proteins. LBPA interactions revealed a strict requirement for a structural calcium tightly bound near the lipid interaction site. Unlike other calcium- and phospholipid-binding proteins, the all-helical triangle-shaped fold of the Bro1 domain confers selectivity for LBPA via a pair of hydrophobic residues in a flexible loop, which undergoes a conformational change upon membrane association. Both LBPA and calcium binding are necessary for endosome association and virus infection, as are ALIX ESCRT binding and dimerization capacity. We conclude that LBPA recruits ALIX onto late endosomes via the calcium-bound Bro1 domain, triggering a conformational change in ALIX to mediate the delivery of viral nucleocapsids to the cytosol during infection.
ALIX 在病毒感染期间的核衣壳释放中发挥作用，溶血磷脂酸 (LBPA) 也是如此。然而，其机制仍不清楚。在这里，我们报告说，LBPA 被 MODA（一种用于发现蛋白质中膜结合区域的算法）预测的 ALIX Bro1 结构域中的暴露位点识别。LBPA 的相互作用揭示了对紧密结合在脂质相互作用位点附近的结构钙的严格要求。与其他钙和磷脂结合蛋白不同，Bro1 结构域的全螺旋三角形折叠通过柔性环中的一对疏水性残基赋予对 LBPA 的选择性，该柔性环在与膜结合时会发生构象变化。LBPA 和钙结合对于内体的结合和病毒感染都是必需的，ALIX ESCRT 结合和二聚化能力也是必需的。我们得出的结论是，LBPA 通过钙结合的 Bro1 结构域将 ALIX 募集到晚期内体上，引发 ALIX 的构象变化，从而在感染过程中将病毒核衣壳递送到细胞质中。
