Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, 1094, Hungary.
Department of Ophthalmology, Semmelweis University, Budapest, 1085, Hungary.
Sci Rep. 2021 Dec 1;11(1):23243. doi: 10.1038/s41598-021-02689-y.
Specific guanine rich nucleic acid sequences can form non-canonical structures, like the four stranded G-quadruplex (GQ). We studied the GQ-forming sequence (named HepB) found in the genome of the hepatitis B virus. Fluorescence-, infrared- and CD-spectroscopy were used. HepB shows a hybrid form in presence of K, but Na, Li, and Rb induce parallel structure. Higher concentrations of metal ions increase the unfolding temperature, which was explained by a short thermodynamic calculation. Temperature stability of the GQ structure was determined for all these ions. Na has stronger stabilizing effect on HepB than K, which is highly unusual. The transition temperatures were 56.6, 53.8, 58.5 and 54.4 °C for Na, K, Li, and Rb respectively. Binding constants for Na and K were 10.2 mM and 7.1 mM respectively. Study of three ligands designed in cancer research for GQ targeting (TMPyP4, BRACO19 and PhenDC3) showed unequivocally their binding to HepB. Binding was proven by the increased stability of the bound form. The stabilization was higher than 20 °C for TMPyP4 and PhenDC3, while it was considerably lower for BRACO19. These results might have medical importance in the fight against the hepatitis B virus.
特定的富含鸟嘌呤的核酸序列可以形成非规范结构，如四链体 G-四链体 (GQ)。我们研究了乙型肝炎病毒基因组中发现的 GQ 形成序列（命名为 HepB）。使用荧光、红外和 CD 光谱法。HepB 在存在 K 的情况下表现出混合形式，但 Na、Li 和 Rb 诱导平行结构。较高浓度的金属离子会增加解折叠温度，这可以通过简短的热力学计算来解释。确定了所有这些离子对 GQ 结构的温度稳定性。与 K 相比，Na 对 HepB 的稳定作用更强，这非常不寻常。Na、K、Li 和 Rb 的转变温度分别为 56.6、53.8、58.5 和 54.4°C。Na 和 K 的结合常数分别为 10.2 mM 和 7.1 mM。研究了在 GQ 靶向癌症研究中设计的三种配体（TMPyP4、BRACO19 和 PhenDC3），它们与 HepB 的结合被明确证明。结合通过结合形式的稳定性增加来证明。TMPyP4 和 PhenDC3 的稳定化作用高于 20°C，而 BRACO19 的稳定化作用则低得多。这些结果在对抗乙型肝炎病毒方面可能具有医学重要性。
