Structural Biology Brussels, and Department of Molecular and Cellular Interactions, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
J Biol Chem. 2010 Feb 19;285(8):5606-13. doi: 10.1074/jbc.M109.068429. Epub 2009 Dec 2.
CcdB(Vfi) from Vibrio fischeri is a member of the CcdB family of toxins that poison covalent gyrase-DNA complexes. In solution CcdB(Vfi) is a dimer that unfolds to the corresponding monomeric components in a two-state fashion. In the unfolded state, the monomer retains a partial secondary structure. This observation correlates well with the crystal and NMR structures of the protein, which show a dimer with a hydrophobic core crossing the dimer interface. In contrast to its F plasmid homologue, CcdB(Vfi) possesses a rigid dimer interface, and the apparent relative rotations of the two subunits are due to structural plasticity of the monomer. CcdB(Vfi) shows a number of non-conservative substitutions compared with the F plasmid protein in both the CcdA and the gyrase binding sites. Although variation in the CcdA interaction site likely determines toxin-antitoxin specificity, substitutions in the gyrase-interacting region may have more profound functional implications.
Vibrio fischeri 的 CcdB(Vfi) 是 CcdB 家族毒素的成员，该家族毒素能使共价结合的拓扑异构酶-DNA 复合物中毒。在溶液中，CcdB(Vfi) 是二聚体，以两态方式展开成相应的单体成分。在展开状态下，单体保留部分二级结构。这一观察结果与该蛋白的晶体和 NMR 结构非常吻合，这些结构显示二聚体具有穿过二聚体界面的疏水性核心。与 F 质粒同源物不同，CcdB(Vfi) 具有刚性的二聚体界面，并且两个亚基的明显相对旋转归因于单体的结构可塑性。与 F 质粒蛋白相比，CcdB(Vfi) 在 CcdA 和拓扑异构酶结合位点都有许多非保守的取代。尽管 CcdA 相互作用位点的变异可能决定了毒素-抗毒素的特异性，但与拓扑异构酶相互作用区域的取代可能具有更深远的功能意义。
