Schoehn G, Fender P, Chroboczek J, Hewat E A
Institut de Biologie Structurale Jean-Pierre Ebel, Grenoble, France.
EMBO J. 1996 Dec 16;15(24):6841-6.
It was recently shown that co-expression of adenovirus type 3 (Ad3) penton base and fibre in the baculovirus system produces dodecahedral particles, as does the expression of the penton base alone. The structure of both of these dodecahedral particles, with and without fibre, has been determined by cryoelectron microscopy and 3-dimensional reconstruction techniques to a resolution of 25 and 20 A, respectively. The general form of the penton base resembles that of the base protein in the recent reconstruction of adenovirus type 2. There is a remarkable difference in the penton base structure with and without the fibre. The five small protuberances on the outer surface of each base move away from the 5-fold axis by approximately 15 A when the fibre is present. These protuberances are of relatively low density and most probably represent a flexible loop possibly containing the RGD site involved in integrin binding. The fibre is apparently bound to the outer surface of the penton base, rather than inserted into it. The fibre is flexible and the shaft contains two distinct globular regions 26 A in diameter. The volume of the inner cavity of the dodecahedron is 350 +/- 100 nm3. This small volume precludes the use of the inner cavity to house genetic information for gene therapy; however, the possibility remains of linking the gene to the dodecahedron surface in the hope that it will be internalized with the dodecahedron.
最近研究表明，在杆状病毒系统中共同表达3型腺病毒（Ad3）的五邻体基座和纤维可产生十二面体颗粒，单独表达五邻体基座时也会产生这种颗粒。已通过冷冻电子显微镜和三维重建技术分别确定了这两种有纤维和无纤维的十二面体颗粒的结构，分辨率分别为25埃和20埃。五邻体基座的总体形态与最近重建的2型腺病毒中的基座蛋白相似。有纤维和无纤维时五邻体基座结构存在显著差异。当有纤维存在时，每个基座外表面的五个小突起会从五重轴向外移动约15埃。这些突起的密度相对较低，很可能代表一个柔性环，可能包含参与整合素结合的RGD位点。纤维显然是结合在五邻体基座的外表面，而不是插入其中。纤维是柔性的，杆部包含两个直径为26埃的不同球状区域。十二面体的内腔体积为350±100立方纳米。如此小的体积排除了利用内腔来容纳基因治疗的遗传信息的可能性；然而，仍有可能将基因连接到十二面体表面，期望它能与十二面体一起被内化。
