Structural basis for gating mechanisms of a eukaryotic P-glycoprotein homolog
Structural basis for gating mechanisms of a eukaryotic P-glycoprotein homolog
复制标题
DOI：
10.1073/pnas.1321562111
复制
发表时间：
2014-03-18
影响因子：
11.1
通讯作者：
Kato, Hiroaki
中科院分区：
文献类型：
--
作者：
Kodan, Atsushi;Yamaguchi, Tomohiro;Kato, Hiroaki
P-糖蛋白是一种ATP结合盒多药转运蛋白，可跨脂质双分子层主动转运多种化学物质。运输的精确分子机制尚未完全了解。在这里，我们提出的晶体结构的真核P-糖蛋白同源物，CmABCB 1 Cyanidioschyzon merolae，在两种形式：在2.6埃分辨率未绑定和绑定到一个独特的变构抑制剂在2.4埃分辨率。抑制剂从外部夹住跨膜螺旋，将CmABCB 1结构固定在类似于未结合结构的向内开放构象中，证实ATP水解循环需要向外开放运动。这些结构，沿着定点突变和转运蛋白活性测量，揭示了转运蛋白的详细结构，包括一个向细胞外侧打开的门和两个向膜内区域和胞质侧打开的门。我们提出，运动的核苷酸结合域驱动这些门控装置通过两个短的细胞内螺旋，IH 1和IH 2，和两个跨膜螺旋，TM 2和TM 5。
P-glycoprotein is an ATP-binding cassette multidrug transporter that actively transports chemically diverse substrates across the lipid bilayer. The precise molecular mechanism underlying transport is not fully understood. Here, we present crystal structures of a eukaryotic P-glycoprotein homolog, CmABCB1 from Cyanidioschyzon merolae, in two forms: unbound at 2.6-angstrom resolution and bound to a unique allosteric inhibitor at 2.4-angstrom resolution. The inhibitor clamps the transmembrane helices from the outside, fixing the CmABCB1 structure in an inward-open conformation similar to the unbound structure, confirming that an outward-opening motion is required for ATP hydrolysis cycle. These structures, along with site-directed mutagenesis and transporter activity measurements, reveal the detailed architecture of the transporter, including a gate that opens to extracellular side and two gates that open to intramembranous region and the cytosolic side. We propose that the motion of the nucleotide-binding domain drives those gating apparatuses via two short intracellular helices, IH1 and IH2, and two transmembrane helices, TM2 and TM5.