Sapp M, Knippers R, Richter A
Nucleic Acids Res. 1986 Sep 11;14(17):6803-20. doi: 10.1093/nar/14.17.6803.
A single strand specific DNA binding protein was purified to homogeneity from calf thymus nucleoprotein. The monomeric protein is elongated in shape and has a molecular mass of 110 kDa. Since immunocytochemistry revealed that the protein is predominantly located in the nucleolus we refer to it as the 110 kDa nucleolar protein. The protein binds not only to single stranded DNA but also to single stranded RNA, including homopolymeric synthetic RNA. We have used the single stranded DNA binding properties of the 110 kDa protein in model studies to investigate its effects on the configuration of nucleic acid. Our results are: only 50-55 protein molecules are sufficient to saturate all binding sites on the 6408 nucleotides of phage fd DNA; protein binding cause a compaction of single stranded DNA; large nucleoprotein aggregates are formed in the presence of divalent cations; this is due to protein-protein interactions which occur at moderately high concentrations of magnesium-, calcium or manganese ions; the protein induces the reassociation of complementary nucleic acid sequences. We speculate that the 110 kDa protein performs similar reactions in vivo and may have a function related to the processing and packaging of preribosomal RNA.
从牛胸腺核蛋白中纯化出一种单链特异性DNA结合蛋白，使其达到同质状态。该单体蛋白呈细长形，分子量为110 kDa。免疫细胞化学显示该蛋白主要位于核仁，因此我们将其称为110 kDa核仁蛋白。该蛋白不仅能与单链DNA结合，还能与单链RNA结合，包括同聚体合成RNA。我们在模型研究中利用110 kDa蛋白的单链DNA结合特性来研究其对核酸构象的影响。我们的结果如下：仅50 - 55个蛋白分子就足以饱和噬菌体fd DNA的6408个核苷酸上的所有结合位点；蛋白结合导致单链DNA压缩；在二价阳离子存在下形成大的核蛋白聚集体；这是由于在中等浓度的镁离子、钙离子或锰离子存在时发生的蛋白质-蛋白质相互作用；该蛋白诱导互补核酸序列重新结合。我们推测110 kDa蛋白在体内执行类似反应，可能具有与前核糖体RNA加工和包装相关的功能。
