Entropic switch regulates myristate exposure in the HIV-1 matrix protein
Entropic switch regulates myristate exposure in the HIV-1 matrix protein
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DOI：
10.1073/pnas.0305665101
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发表时间：
2004-01-13
影响因子：
11.1
通讯作者：
Summers, MF
中科院分区：
文献类型：
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作者：
Tang, C;Loeliger, E;Summers, MF
HIV 的肉豆蔻酰化基质蛋白 (myr-MA) 作为细胞内定位的调节剂，在病毒组装过程中将 Gag 前体多蛋白靶向质膜中的脂筏，并在感染过程中从膜上解离，以实现预整合复合物的核靶向。膜释放是由 Gag 的蛋白水解裂解触发的，到目前为止，人们一直认为蛋白水解会诱导 myr-MA 发生构象变化，从而隔离肉豆蔻基。此处报道的 NMR 研究表明，正如预期的那样，myr-MA 采用 myr 暴露的 [myr(e)] 和隔离的 [myr(s)] 状态。出乎意料的是，两种状态下蛋白质的三级结构非常相似，隔离的肉豆蔻基占据一个空腔，只需进行微小的构象调整即可插入。此外，肉豆蔻酸酯暴露与三聚化相结合，肉豆蔻基基团隔离在单体中并暴露在三聚体中（K-assoc = 2.5 +/- 0.6 x 10(8) M-2）。平衡常数向包含衣壳结构域的 Gag 样构建体中的三聚体、肉豆蔻酸酯暴露物种移动了大约 20 倍，表明促进自缔合的 Gag 子结构域增强了暴露。我们的研究结果表明，HIV-1 肉豆蔻基开关不是通过机械诱导的构象变化（如其他肉豆蔻基开关所观察到的）来调节，而是通过预先存在的平衡的熵调节来调节。
The myristoylated matrix protein (myr-MA) of HIV functions as a regulator of intracellular localization, targeting the Gag precursor polyprotein to lipid rafts in the plasma membrane during virus assembly and dissociating from the membrane during infectivity for nuclear targeting of the preintegration complex. Membrane release is triggered by proteolytic cleavage of Gag, and it has, until now, been believed that proteolysis induces a conformational change in myr-MA that sequesters the myristyl group. NMR studies reported here reveal that myr-MA adopts myr-exposed [myr(e)] and -sequestered [myr(s)] states, as anticipated. Unexpectedly, the tertiary structures of the protein in both states are very similar, with the sequestered myristyl group occupying a cavity that requires only minor conformational adjustments for insertion. In addition, myristate exposure is coupled with trimerization, with the myristyl group sequestered in the monomer and exposed in the trimer (K-assoc = 2.5 +/- 0.6 x 10(8) M-2). The equilibrium constant is shifted approximate to20-fold toward the trimeric, myristate-exposed species in a Gag-like construct that includes the capsid domain, indicating that exposure is enhanced by Gag subdomains that promote self-association. Our findings indicate that the HIV-1 myristyl switch is regulated not by mechanically induced conformational changes, as observed for other myristyl switches, but instead by entropic modulation of a preexisting equilibrium.