Alazard R, Ebel C, Venien-Bryan V, Mourey L, Samama J P, Chandler M
Laboratoire de Microbiologie et de Génétique Moléculaires, CNRS, Toulouse, France.
Eur J Biochem. 1998 Mar 15;252(3):408-15. doi: 10.1046/j.1432-1327.1998.2520408.x.
The regulation of the lytic and lysogenic development in the life cycle of bacteriophage Mu is regulated in part by its repressor, c, which binds to three operator sites, O1, O2 and O3, overlapping two divergent promoters. The oligomeric structure of this repressor protein was investigated by hydrodynamic and biochemical methods. Size-exclusion chromatography, analytical ultracentrifugation, dynamic light scattering, crosslinking and direct electron microscopy observations suggest that c exists primarily as a hexamer with a molecular mass of 120-140 kDa at low concentrations, i.e. in the 10-microM range. This molecule undergoes a self-assembly process leading to dodecamers and higher order species as the concentration is further increased in a manner depending on the nature of the solvent. Our results also suggest that these species have an elongated structure, and a possible arrangement of the subunits within the hexamer is proposed. The implication of this unusual quaternary structure for a repressor in its interaction with the operator sites O1 and O2 remains to be elucidated.
噬菌体Mu生命周期中裂解和溶原发育的调控部分受其阻遏物c的调节，c与三个操纵位点O1、O2和O3结合，这三个位点与两个 divergent 启动子重叠。通过流体动力学和生化方法研究了这种阻遏蛋白的寡聚结构。尺寸排阻色谱、分析超速离心、动态光散射、交联和直接电子显微镜观察表明，在低浓度下，即10微摩尔范围内，c主要以分子量为120-140 kDa的六聚体形式存在。随着浓度进一步增加，该分子会经历一个自组装过程，形成十二聚体和更高阶的物种，其方式取决于溶剂的性质。我们的结果还表明，这些物种具有细长的结构，并提出了六聚体内亚基的一种可能排列方式。这种不寻常的四级结构对阻遏物与操纵位点O1和O2相互作用的影响仍有待阐明。
