Visualization of α-helices in a 6-angstrom resolution cryoelectron microscopy structure of adenovirus allows refinement of capsid protein assignments
Visualization of α-helices in a 6-angstrom resolution cryoelectron microscopy structure of adenovirus allows refinement of capsid protein assignments
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DOI：
10.1128/jvi.01652-06
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发表时间：
2006-12-01
影响因子：
5.4
通讯作者：
Stewart, Phoebe L.
中科院分区：
文献类型：
--
作者：
Saban, Susan D.;Silvestry, Mariena;Stewart, Phoebe L.
利用低温电子显微镜（cryoEM）单粒子图像重建技术确定腺病毒的结构，分辨率为6埃。六方基和五边形基晶体结构与低温电镜密度的对接建立了10个或更多残基的α螺旋被分解为棒。通过从低温电镜重建中减去假原子衣壳，计算出差分图。根据目前缺乏原子分辨率结构的额外衣壳蛋白（蛋白IIIa， VI， VIII和IX）所观察到的α -螺旋和二级结构预测来分析所得密度。被预测为高度α -螺旋的蛋白IIIa，被分配到在内衣壳表面的五边形底部观察到的一簇螺旋上。蛋白质VI在每个六体三聚体中有1.5个拷贝，预计有两个长α螺旋，其中一个似乎位于六体腔内。蛋白VIII被腺病毒蛋白酶切割成7.6和12.1 kDa的两个片段，预测较大的片段具有一个长α -螺旋，这与观察到的蛋白VIII在内衣壳表面的密度一致。据预测，蛋白IX有一个长α -螺旋，它也有强烈的倾向于盘绕线圈的形成。面边缘附近的密度区域现在被分解为一个四螺旋束，并被分配给蛋白IX的c端α -螺旋的四个拷贝。
The structure of adenovirus was determined to a resolution of 6 angstrom by cryoelectron microscopy (cryoEM) single-particle image reconstruction. Docking of the hexon and penton base crystal structures into the cryoEM density established that alpha-helices of 10 or more residues are resolved as rods. A difference map was calculated by subtracting a pseudoatomic capsid from the cryoEM reconstruction. The resulting density was analyzed in terms of observed alpha-helices and secondary structure predictions for the additional capsid proteins that currently lack atomic resolution structures (proteins IIIa, VI, VIII, and IX). Protein IIIa, which is predicted to be highly alpha-helical, is assigned to a cluster of helices observed below the penton base on the inner capsid surface. Protein VI is present in similar to 1.5 copies per hexon trimer and is predicted to have two long alpha-helices, one of which appears to lie inside the hexon cavity. Protein VIII is cleaved by the adenovirus protease into two fragments of 7.6 and 12.1 kDa, and the larger fragment is predicted to have one long alpha-helix, in agreement with the observed density for protein VIII on the inner capsid surface. Protein IX is predicted to have one long alpha-helix, which also has a strongly indicated propensity for coiled-coil formation. A region of density near the facet edge is now resolved as a four-helix bundle and is assigned to four copies of the C-terminal alpha-helix from protein IX.