Llamas-Saiz A L, Agbandje-McKenna M, Parker J S, Wahid A T, Parrish C R, Rossmann M G
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
Virology. 1996 Nov 1;225(1):65-71. doi: 10.1006/viro.1996.0575.
A single mutation in canine parvovirus (CPV) of VP2 residue 300 from alanine to aspartic acid causes a loss of canine host range and alters the antigenic properties of the virus. The three-dimensional structure of this mutant has been solved to 3.25 A resolution. Crystals of full particles were triclinic, with cell dimensions of a = 267.6, b = 268.5, c = 274.3 A. alpha = 61.9, beta = 62.6, and gamma = 60.2 degrees. The native structure of CPV was used as an initial model. Phases were improved by real-space electron density averaging. In spite of the relative low percentage of observed reflections (32.5% of the data between 15.0 and 3.25 A resolution), the presence of 60-fold noncrystallographic redundancy allowed the averaging procedure to converge smoothly. The mutant aspartic acid at residue 300 forms a salt bridge with Arg81 in an icosahedrally threefold-related subunit, inducing local changes within the antigenic site B on the CPV surface. In addition, the loop between residues 359 and 374 adopts a conformation similar to that displayed by feline panleukopenia virus. The ability of the Ala300-->Asp mutant to evade antibody binding can be associated with the change of charge distribution and structure in the antigenic binding site. The variation in host range behavior may be due to the increased stability as a result of formation of the salt bridge between adjacent subunits.
犬细小病毒（CPV）VP2 残基 300 处由丙氨酸突变为天冬氨酸的单一突变导致犬宿主范围丧失，并改变了病毒的抗原特性。该突变体的三维结构已解析至 3.25 Å 分辨率。完整颗粒的晶体为三斜晶系，晶胞参数为 a = 267.6、b = 268.5、c = 274.3 Å，α = 61.9°、β = 62.6°、γ = 60.2°。CPV 的天然结构用作初始模型。通过实空间电子密度平均法改善相位。尽管观测到的反射百分比相对较低（在 15.0 至 3.25 Å 分辨率之间的数据占 32.5%），但 60 倍的非晶体学冗余度使得平均过程能够顺利收敛。残基 300 处的突变天冬氨酸在二十面体三重相关亚基中与 Arg81 形成盐桥，诱导 CPV 表面抗原位点 B 内的局部变化。此外，残基 359 和 374 之间的环采用与猫泛白细胞减少症病毒相似的构象。Ala300→Asp 突变体逃避抗体结合的能力可能与抗原结合位点电荷分布和结构的变化有关。宿主范围行为的变化可能是由于相邻亚基之间形成盐桥导致稳定性增加所致。
