Department of Biochemistry and Molecular Biology, George S Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
Proc Natl Acad Sci U S A. 2010 Jun 15;107(24):10908-13. doi: 10.1073/pnas.0914717107. Epub 2010 Jun 1.
The trimeric human copper transporter 1 (hCTR1) is essential for copper uptake and is implicated in sensitivity to chemotherapy drugs. Using the cryoelectron microscopy (cryoEM) map of hCTR1 and evolutionary data, we constructed a Calpha-trace model of the membrane region. The model structure, supported by mutagenesis data, was used to investigate global dynamics through elastic network models. Identified as dominant hinge regions, hCTR1's MxxxM and GxxxG motifs were shown to have significant roles in functional movements characterized by the two slowest modes of motion. Both modes predicted significant changes at the wide cytoplasmic pore region; the slowest mode introduced a rotational motion around the pore central axis, whereas in the following mode the cytoplasmic parts of the helices approached and moved away from the pore center. In the most cooperative mode, the MxxxM motif in the extracellular narrow region remained static. The second mode of motion, however, predicted a cooperative rotational motion of this copper-binding motif, possibly reflecting activation at the pore's extracellular entrance. We suggest a molecular mechanism of copper transport in which this motif serves both as a gate and as a selectivity filter. We also suggest residues that are responsible for pH activation.
人源三聚物铜转运蛋白 1（hCTR1）对于铜的摄取至关重要，并与化疗药物的敏感性有关。利用 hCTR1 的冷冻电镜（cryoEM）图谱和进化数据，我们构建了跨膜区域的α-碳追踪模型。该模型结构得到了突变数据的支持，并通过弹性网络模型研究了全局动力学。确定为主要铰链区域的 hCTR1 的 MxxxM 和 GxxxG 基序在两个最慢的运动模式所描述的功能运动中具有重要作用。这两种模式都预测了宽细胞质孔区域的显著变化；最慢的模式在孔中心轴周围引入了旋转运动，而在下一个模式中，螺旋的细胞质部分靠近并远离孔中心。在最合作的模式中，细胞外狭窄区域的 MxxxM 基序保持静态。然而，第二种运动模式预测了这个铜结合基序的协同旋转运动，可能反映了孔的细胞外入口的激活。我们提出了一种铜转运的分子机制，其中这个基序既是一个门，也是一个选择性过滤器。我们还提出了负责 pH 激活的残基。
