Acta Phys. -Chim. Sin. ›› 2018, Vol. 34 ›› Issue (11): 1293-1298.doi: 10.3866/PKU.WHXB201804111

Special Issue: 庆祝李永舫院士七十华诞特刊

• ARTICLE • Previous Articles    

K+ Concentration-Dependent Conformational Change of Pb2+-Stabilized G-quadruplex

Ze YU1,Xiaohong LI1,*(),Yunchao LI1,*(),Mingfu YE2,*()   

  1. 1 College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
    2 School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, 243002, Anhui Province, P. R. China
  • Received:2018-02-26 Published:2018-04-17
  • Contact: Xiaohong LI,Yunchao LI,Mingfu YE E-mail:lxhxiao@bnu.edu.cn;liyc@bnu.edu.cn;yemingfu@ahut.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21673022)

Abstract:

DNA can adopt a diverse range of structural conformations, including duplexes, triplexes, and quadruplexes. Among these structures, G-quadruplexes have attracted much more attention of researchers. For G-rich DNA sequences, they can fold into multiple G-quadruplex conformations, such as parallel, antiparallel, or hybrid, and the exact conformation is influenced by G-rich DNA sequence, strand concentration, and binding cations. Among the factors influencing the G-quadruplex conformation and stability, cations played a really important role. Numerous studies have reported cation-dependent stability and topological changes of G-quadruplexes; however, most of studies have focused on the effect of individual cation (such as charge, radii, or hydration, etc.), and only few have assessed the effect of competition between cations at different concentrations. Actually, most biological and aqueous systems contained multiple cations and each of the cations had very different concentrations. Thus, investigation of the competitions between different cations (at different concentrations) for binding with G-quadruplexes and their effects on polymorphism of G-quadruplex is critical, which would improve our understanding of the roles of G-quadruplexes and assist us in further exploring their potential applications in biochemical, biomedical, and environmental systems. Under this situation, we focused on K+- and Pb2+-stabilized G-quadruplex, two major cations that are usually used to stabilize G-quadruplex. It has been shown that for a given G-quadruplex forming DNA sequence, Pb2+-stabilized G-quadruplex was more stable than K+-stabilized G-quadruplex, and Pb2+ could substitute K+ in K+-stabilized G-quadruplex. However, the concentrations of K+ that allow such a substitution are not completely studied. Previous studies have used G-quadruplex-based fluorescent, colorimetric, and electrochemical sensors for detecting Pb2+, and these methods show excellent selectivity for Pb2+ over K+. Although G-quadruplex-based Pb2+ sensors were developed, their applications in real samples containing K+ were greatly limited. Thus, how K+ and Pb2+ compete for binding to G-quadruplex and how K+ concentrations affect the stability of Pb2+-stabilized G-quadruplex remain elusive. In this study, eight G-rich DNA sequences were selected to investigate the effect of K+ concentration on Pb2+-stabilized G-quadruplex. Previous studies have established that the presence of K+ cannot alter the stability of Pb2+-stabilized G-quadruplex. In contrast to this, our results indicated that K+ could induce a conformational switch in Pb2+-stabilized T2TT (G-rich DNA sequence, forming G-quadruplex in the presence of Pb2+), and further replace Pb2+ in Pb2+-stabilized T2TT and transform it into 2K+-stabilized T2TT, which is strictly K+ concentration-dependent. Importantly, such a conformational switch could be observed for other seven selected G-rich sequences as well. Therefore, our findings provide a new insight into the exchange and competition of cations in G-quadruplex.

Key words: Lead ion, Potassium ion, G-quadruplex, G-rich DNA sequence, Conformational switch

MSC2000: 

  • O641.3