The exterior minor protein IX of adenoviruses (AdVs) is a frequent target of attachment of antigens and the modified AdVs are being used as potent vaccine platforms. The organization of protein IX is disticntly different between human adenoviruses (HAdVs) and non-HAdVs. The analysis of solvent accessibility, based on the near atomic resolution structures, suggests that the C-terminal residues of IX are more accessible in non-HAdVs (e.g., bovine adenovirus) than in HAdVs. Although the C-terminal fusions of IX are displayed on the capsid surface, they could disrupt the formation of tetrameric coiled-coils (4-HLXB) in HAdVs due to steric hinderance, thereby potentially affecting the capsid stability. Importantly, the parallel-antiparallel arrangement of helices seen in the 4-HLXB is not condusive for IX C-terminal fusions in HAdVs. In contrast, the parallel trimeric C-terminal coiled-coils in non-HAdVs are unlikely to be affected by the attachment of antigens and more efficiently displayed on the AdV surface.

腺病毒（AdVs）的外部次要蛋白IX是抗原附着的常见目标，并且修饰的AdVs被用作有效的疫苗平台。在人腺病毒（HAdV）和非HAdV之间，蛋白质IX的组织明显不同。基于接近原子拆分结构的溶剂可及性分析表明，IX的C末端残基在非HAdV（例如​​牛腺病毒）中比在HAdV中更易接近。尽管IX的C端融合物显示在衣壳表面上，但由于空间位阻，它们可能破坏HAdV中四聚体卷曲螺旋（4-HLXB）的形成，从而潜在地影响衣壳的稳定性。重要的是，在4-HLXB中看到的螺旋的平行-反平行排列对HAdV中的IX C端融合不利。相比之下，