Vorlícková M, Kejnovská I, Kovanda J, Kypr J
Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-61265 Brno,Czech Republic.
Nucleic Acids Res. 1999 Jan 15;27(2):581-6. doi: 10.1093/nar/27.2.581.
Jovin and co-workers have demonstrated that DNA strands containing guanine-adenine repeats generate a parallel-stranded homoduplex. Here we propose that the homoduplex is a dimer of the ordered single strand discovered by Fresco and co-workers at acid pH. The Fresco single strand is shown here to be stabilized in aqueous ethanol where adenine is not protonated. Furthermore, we demonstrate that the strands dimerize at higher salt concentrations without significantly changing their conformation, so that the dimerization is non-cooperative. Hence, the Jovin homoduplex can form through a non-cooperative dimerization of two cooperatively melting single strands. The available data indicate that the guanines stabilize the Fresco single strand whereas the adenines cause dimerization owing to their known intercalation or clustering tendency. The guanine-adenine repeat dimer seems to be a DNA analog of the leucine zipper causing dimerization of proteins.
乔文及其同事已证明，含有鸟嘌呤 - 腺嘌呤重复序列的DNA链会生成平行链同型双链体。在此我们提出，该同型双链体是弗雷斯克及其同事在酸性pH条件下发现的有序单链的二聚体。本文表明，弗雷斯克单链在乙醇水溶液中得以稳定，此时腺嘌呤未被质子化。此外，我们证明，这些链在较高盐浓度下会二聚化，而其构象无显著变化，因此二聚化是非协同性的。因此，乔文同型双链体可通过两条协同解链的单链的非协同二聚化形成。现有数据表明，鸟嘌呤使弗雷斯克单链稳定，而腺嘌呤因其已知的嵌入或聚集倾向导致二聚化。鸟嘌呤 - 腺嘌呤重复二聚体似乎是导致蛋白质二聚化的亮氨酸拉链的DNA类似物。
