G-quadruplexes have become attractive drug targets in cancer therapy. However, due to the polymorphism of G-quadruplex structures, it is difficult to experimentally verify the relevant structures of multiple intermediates and transition states in dynamic equilibrium. Hence, understanding the mechanism by which structural conversions of G-quadruplexes occur is still challenging. We conducted targeted molecular dynamics simulation with umbrella sampling to investigate how salt affects the conformational conversion of human telomeric G-quadruplex. Our results explore a unique view into the structures and energy barrier of the intermediates and transition states in the interconversion process. The pathway of G-quadruplex conformational interconversion was mapped out by a free energy landscape, consisting of branched parallel pathways with multiple energy basins. We propose a salt-controlled mechanism that as the salt concentration increases, the conformational conversion mechanism switches from multi-pathway folding to sequential folding pathways. The hybrid-I and hybrid-II structures are intermediates in the basket-propeller transformation. In high-salt solutions, the conformational conversion upon K⁺ binding is more feasible than upon Na⁺ binding. The free energy barrier for conformational conversions ranges from 1.6 to 4.6 kcal/mol. Our work will be beneficial in developing anticancer agents.

G-四链体已成为癌症治疗中有吸引力的药物靶点。然而，由于G-四链体结构的多态性，很难通过实验验证动态平衡中多个中间体和过渡态的相关结构。因此，了解 G-四链体结构转换发生的机制仍然具有挑战性。我们使用伞状采样进行了靶向分子动力学模拟，以研究盐如何影响人类端粒 G-四链体的构象转换。我们的结果探索了对互变过程中中间体和过渡态的结构和能垒的独特看法。G-四链体构象相互转换的途径由自由能图谱绘制，由具有多个能量盆地的分支平行路径组成。我们提出了一种盐控制机制，随着盐浓度的增加，构象转换机制从多途径折叠转变为顺序折叠途径。混合 I 和混合 II 结构是篮式螺旋桨转换的中间体。在高盐溶液中，K 的构象转换⁺结合比 Na ⁺结合更可行。构象转换的自由能垒范围为 1.6 至 4.6 kcal/mol。我们的工作将有利于开发抗癌药物。