Strelkov S V, Tao Y, Shneider M M, Mesyanzhinov V V, Rossmann M G
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1392, USA.
Acta Crystallogr D Biol Crystallogr. 1998 Sep 1;54(Pt 5):805-16. doi: 10.1107/s0907444997018878.
Fibritin, a 52 kDa product of bacteriophage T4 gene wac, forms 530 A long fibers, named whiskers, that attach to the phage neck and perform a helper function during phage assembly. Fibritin is a homotrimer, with its predominant central domain consisting of 12 consecutive alpha-helical coiled-coil segments linked together by loops. The central domain is flanked by small globular domains at both ends. Fibritin M is a genetically engineered fragment of the wild type and contains 74 amino-acid residues corresponding to the last coiled-coil segment and the complete carboxy-terminal domain. The crystals of fibritin M belong to the rare space group P3 with three crystallographically independent trimers in the unit cell. The structure has been established at 1.85 A resolution by combining molecular and isomorphous replacement techniques. One of the two heavy-atom derivatives used was gaseous xenon. A substantial fraction of residues in each independent trimer is disordered to various extents in proportion to the lack of restraints on the molecules provided by the lattice contacts. Accurate modeling of the solvent present in the crystals was crucial for achieving good agreement with experimental data.
纤维蛋白是噬菌体T4基因wac的一种52 kDa产物，它能形成530 Å长的纤维，即须晶，这些须晶附着在噬菌体颈部，并在噬菌体组装过程中发挥辅助功能。纤维蛋白是一种同三聚体，其主要的中央结构域由12个连续的α-螺旋卷曲螺旋片段通过环连接而成。中央结构域的两端是小的球状结构域。纤维蛋白M是野生型的基因工程片段，包含74个氨基酸残基，对应于最后一个卷曲螺旋片段和完整的羧基末端结构域。纤维蛋白M的晶体属于罕见的空间群P3，晶胞中有三个晶体学上独立的三聚体。通过结合分子置换和同晶置换技术，该结构已在1.85 Å分辨率下确定。所使用的两种重原子衍生物之一是气态氙。每个独立三聚体中的相当一部分残基在不同程度上无序排列，这与晶格接触对分子提供的约束不足成比例。准确模拟晶体中存在的溶剂对于与实验数据达成良好一致至关重要。
