Nguyen Thanh H, Vidovszky Márton Z, Ballmann Mónika Z, Sanz-Gaitero Marta, Singh Abhimanyu K, Harrach Balázs, Benkő Mária, van Raaij Mark J
Departamento de Estructura de Macromoleculas, Centro Nacional de Biotecnologia (CNB-CSIC), calle Darwin 3, 28049, Madrid, Spain.
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary.
Virol J. 2015 May 22;12:81. doi: 10.1186/s12985-015-0309-1.
In adenoviruses, primary host cell recognition is generally performed by the head domains of their homo-trimeric fibre proteins. This first interaction is reversible. A secondary, irreversible interaction subsequently takes place via other adenovirus capsid proteins and leads to a productive infection. Although many fibre head structures are known for human mastadenoviruses, not many animal adenovirus fibre head structures have been determined, especially not from those belonging to adenovirus genera other than Mastadenovirus.
We constructed an expression vector for the fibre head domain from a ruminant atadenovirus, bovine adenovirus 4 (BAdV-4), consisting of amino acids 414-535, expressed the protein in Escherichia coli, purified it by metal affinity and cation exchange chromatography and crystallized it. The structure was solved using single isomorphous replacement plus anomalous dispersion of a mercury derivative and refined against native data that extended to 1.2 Å resolution.
Like in other adenoviruses, the BAdV-4 fibre head monomer contains a beta-sandwich consisting of ABCJ and GHID sheets. The topology is identical to the fibre head of the other studied atadenovirus, snake adenovirus 1 (SnAdV-1), including the alpha-helix in the DG-loop, despite of them having a sequence identity of only 15 %. There are also differences which may have implications for ligand binding. Beta-strands G and H are longer and differences in several surface-loops and surface charge are observed.
Chimeric adenovirus fibres have been used to retarget adenovirus-based anti-cancer and gene therapy vectors. Ovine adenovirus 7 (OAdV-7), another ruminant atadenovirus, is intensively tested as a basis for such a vector. Here, we present the high-resolution atomic structure of the BAdV-4 fibre head domain, the second atadenovirus fibre head structure known and the first of an atadenovirus that infects a mammalian host. Future research should focus on the receptor-binding properties of these fibre head domains.
在腺病毒中，主要宿主细胞识别通常由其三聚体纤维蛋白的头部结构域完成。这种初次相互作用是可逆的。随后通过其他腺病毒衣壳蛋白发生二次不可逆相互作用，并导致有效感染。虽然已知许多人 Mastadenovirus 属腺病毒的纤维头部结构，但已确定的动物腺病毒纤维头部结构并不多，尤其是那些不属于 Mastadenovirus 属的腺病毒。
我们构建了一个用于反刍动物腺病毒 4（BAdV-4）纤维头部结构域的表达载体，该结构域由氨基酸 414 - 535 组成，在大肠杆菌中表达该蛋白，通过金属亲和层析和阳离子交换层析进行纯化并结晶。使用单同晶置换加汞衍生物的反常色散法解析结构，并根据分辨率扩展至 1.2 Å 的天然数据进行精修。
与其他腺病毒一样，BAdV-4 纤维头部单体包含一个由 ABCJ 和 GHID 片层组成的β-三明治结构。尽管它们的序列同一性仅为 15%，但其拓扑结构与另一种已研究的禽腺病毒蛇腺病毒 1（SnAdV-1）的纤维头部相同，包括 DG 环中的α-螺旋。也存在一些可能对配体结合有影响的差异。β-链 G 和 H 更长，并且在几个表面环和表面电荷上观察到差异。
嵌合腺病毒纤维已被用于重新靶向基于腺病毒的抗癌和基因治疗载体。另一种反刍动物腺病毒绵羊腺病毒 7（OAdV-7）作为此类载体的基础正在进行深入测试。在此，我们展示了 BAdV-4 纤维头部结构域的高分辨率原子结构，这是已知的第二个禽腺病毒纤维头部结构，也是感染哺乳动物宿主的禽腺病毒中的第一个。未来的研究应集中在这些纤维头部结构域的受体结合特性上。
