The crystal structure of the CmABCB1 G132V mutant, which favors the outward‐facing state, reveals the mechanism of the pivotal joint between TM1 and TM3
The crystal structure of the CmABCB1 G132V mutant, which favors the outward‐facing state, reveals the mechanism of the pivotal joint between TM1 and TM3
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DOI：
10.1002/pro.4058
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发表时间：
2021-03
期刊：
影响因子：
8
通讯作者：
K. Matsuoka;T. Nakatsu;H. Kato
中科院分区：
文献类型：
--
作者：
K. Matsuoka;T. Nakatsu;H. Kato
CmABCB 1是人P-糖蛋白的同源物，其通过向内和向外状态之间的构象变化的迭代循环挤出各种底物。CmABCB 1的内向和外向结构的比较表明，跨膜结构域中的枢轴关节调节跨膜螺旋的倾斜。跨膜螺旋1（TM 1）在TM 1 -3连接处与TM 3形成紧密的螺旋-螺旋接触。在TM 1 -3关节处Gly 132突变为缬氨酸，G132 V，导致ATP酶活性增加10倍，但这种变化背后的机制仍不清楚。在这里，我们报告了CmABCB 1 G132 V突变体的外向状态的晶体结构，分辨率为2.15 nm。我们在TM 1 -3关节周围区域观察到G132 V的外向状态与前一个状态之间的结构位移，以及细胞外门的显著扩张。我们推测，由瓦尔取代引起的空间位阻使构象平衡向外向状态移动，有利于核苷酸结合结构域的二聚体状态，从而增加G132 V突变体的ATP酶活性。
CmABCB1 is a homologue of human P‐glycoprotein, which extrudes various substrates by iterative cycles of conformational changes between the inward‐ and outward‐facing states. Comparison of the inward‐ and outward‐facing structures of CmABCB1 suggested that pivotal joints in the transmembrane domain regulate the tilt of transmembrane helices. Transmembrane helix 1 (TM1) forms a tight helix–helix contact with TM3 at the TM1–3 joint. Mutation of Gly132 to valine at the TM1–3 joint, G132V, caused a 10‐fold increase in ATPase activity, but the mechanism underlying this change remains unclear. Here, we report a crystal structure of the outward‐facing state of the CmABCB1 G132V mutant at a 2.15 Å resolution. We observed structural displacements between the outward‐facing states of G132V and the previous one at the region around the TM1–3 joint, and a significant expansion at the extracellular gate. We hypothesize that steric hindrance caused by the Val substitution shifted the conformational equilibrium toward the outward‐facing state, favoring the dimeric state of the nucleotide‐binding domains and thereby increasing the ATPase activity of the G132V mutant.