Three-dimensional fold of the human AQP1 water channel determined at 4 A resolution by electron crystallography of two-dimensional crystals embedded in ice.
Three-dimensional fold of the human AQP1 water channel determined at 4 A resolution by electron crystallography of two-dimensional crystals embedded in ice.
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DOI：
10.1006/jmbi.2000.3949
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发表时间：
2000-08
影响因子：
5.6
通讯作者：
G. Ren;A. Cheng;V. Reddy;P. Melnyk;A. Mitra
中科院分区：
文献类型：
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作者：
G. Ren;A. Cheng;V. Reddy;P. Melnyk;A. Mitra
在这里，我们提出了一个三维（3D）密度图的去糖基化，人红细胞水通道蛋白1（AQP 1）确定在4 A的分辨率在平面上和约7 A的分辨率垂直于双层。通过分析记录自脂质双层膜中的AQP 1的倾斜（高达60度）、冰包埋、冷冻水合的2D晶体的图像和电子衍射图案来计算该图。该图谱显著扩展了我们在较低（7埃×约20埃）分辨率下确定的与AQP 1多肽链折叠相关的发现。单体内的溶剂可及体积具有前庭结构，在双层中心附近具有狭窄的直径约6.5 A的收缩，其中假定存在水选择性通道的位置。跨膜螺旋的清晰分辨的密度显示了大体积侧链的预期突起。螺旋桶内部的密度（假定的NPA盒区域）与我们以前的图谱相比更好地分辨，表明与一些螺旋的联系更清楚，并且它可能含有短的α-螺旋。在双层末端，一些螺旋间亲水环的密度是可见的。与这些观察到的螺旋间连接一致，可能的模型为AQP 1多肽链的线程。一个优选的模型推导出一组芳香族残基的氨基酸序列和3D密度图中的推定位置一致。
Here, we present a three-dimensional (3D) density map of deglycosylated, human erythrocyte aquaporin 1 (AQP1) determined at 4 A resolution in plane and approximately 7 A resolution perpendicular to the bilayer. The map was calculated by analyzing images and electron diffraction patterns recorded from tilted (up to 60 degrees ), ice-embedded, frozen-hydrated 2D crystals of AQP1 in lipid bilayer membranes. This map significantly extends the findings related to the folding of the AQP1 polypeptide chain determined by us at a lower, 7 A by approximately 20 A, resolution. The solvent-accessible volume within a monomer has a vestibular architecture, with a narrow, approximately 6.5 A diameter constriction near the center of the bilayer, where the location of the water-selective channel is postulated to exist. The clearly resolved densities for the transmembrane helices display the protrusions expected for bulky side-chains. The density in the interior of the helix barrel (putative NPA box region) is better resolved compared to our previous map, suggesting clearer linkage to some of the helices, and it may harbor short stretches of alpha-helix. At the bilayer extremities, densities for some of the inter-helix hydrophilic loops are visible. Consistent with these observed inter-helix connections, possible models for the threading of the AQP1 polypeptide chain are presented. A preferred model is deduced that agrees with the putative locations of a group of aromatic residues in the amino acid sequence and in the 3D density map.