Structural basis for targeting HIV-1 Gag proteins to the plasma membrane for virus assembly
Structural basis for targeting HIV-1 Gag proteins to the plasma membrane for virus assembly
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DOI：
10.1073/pnas.0602818103
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发表时间：
2006-07-25
影响因子：
11.1
通讯作者：
Summers, Michael F.
中科院分区：
文献类型：
--
作者：
Saad, Jamil S.;Miller, Jaime;Summers, Michael F.
在HIV-1复制的后期，新合成的逆转录病毒Gag蛋白靶向大多数造血细胞类型的质膜，在脂筏上共定位并组装成未成熟的病毒粒子。膜结合是由Gag的基质（MA）结构域介导的，Gag是一种含有n端肉豆蔻酰基的132个残基多肽，可以采用隔离和暴露的构象。虽然已知暴露可促进膜结合，但Gag靶向特定膜的机制尚未确定。最近的研究表明，磷脂柱醇（PI） 4,5-二磷酸[Pl(45)P-2]是一种调节细胞蛋白向质膜定位的因子，也调节Gag的定位和组装[Ono， a ., Ablan， S. D., Lockett， S. j ., Nagashima， K. & Freed， E. O. (2004) Proc. Natl。国家科学。[j]。在这里，我们发现Pl(4,5)P2直接与HIV-1 MA结合，诱导引发肉豆蔻酸暴露的构象变化。相关的磷脂酰亚肽PI、PI(3)P、PI(4)P、PI(S)P和PI(3,5)P2与MA没有明显的亲和力或触发肉豆蔻酸暴露。结构研究表明，PI(4,5)P2采用“延伸脂质”构象，其中肌醇头部基团和2'-脂肪酸链结合到疏水性裂缝上，1'-脂肪酸和暴露的肉豆醇基团覆盖在先前涉及膜结合的保守的基本表面斑块上。我们的研究结果表明，PI(4,5)P2既是肉豆蔻细胞开关的触发器，也是膜锚，这表明了将Gag靶向膜筏的潜在机制。
During the late phase of HIV type 1 (HIV-1) replication, newly synthesized retroviral Gag proteins are targeted to the plasma membrane of most hematopoietic cell types, where they colocalize at lipid rafts and assemble into immature virions. Membrane binding is mediated by the matrix (MA) domain of Gag, a 132-residue polypeptide containing an N-terminal myristyl group that can adopt sequestered and exposed conformations. Although exposure is known to promote membrane binding, the mechanism by which Gag is targeted to specific membranes has yet to be established. Recent studies have shown that phosphaticylinositol (PI) 4,5-bisphosphate [Pl(45)P-2], a factor that regulates localization of cellular proteins to the plasma membrane, also regulates Gag localization and assembly [Ono, A., Ablan, S. D., Lockett, S.J., Nagashima, K. & Freed, E. O. (2004) Proc. Natl. Acad Sci. USA 101, 14889-14894]. Here we show that Pl(4,5)P2 binds directly to HIV-1 MA, inducing a conformational change that triggers myristate exposure. Related phosphatidylinositides PI, PI(3)P, PI(4)P, PI(S)P, and PI(3,5)P2 do not bind MA with significant affinity or trigger myristate exposure. Structural studies reveal that PI(4,5)P2 adopts an "extended lipid" conformation, in which the inositol head group and 2'-fatty acid chain bind to a hydrophobic cleft, and the 1'-fatty acid and exposed myristyl group bracket a conserved basic surface patch previously implicated in membrane binding. Our findings indicate that PI(4,5)P2 acts as both a trigger of the myristyl switch and a membrane anchor and suggest a potential mechanism for targeting Gag to membrane rafts.