Structural transitions of a GG‐platinated DNA duplex induced by pH, temperature and box A of high‐mobility‐group protein 1

摘要: [1H,15N] and 1H NMR, and CD spectroscopy are used to show that the duplex d(A‐T‐A‐C‐A‐T‐Pt7G‐Pt7G‐T‐A‐C‐A‐T‐A) ˙ d(T‐A‐T‐G‐T‐A‐C‐C‐A‐T‐G‐T‐A‐T), where Pt7G is platinated guanine, containing the cis‐[Pt(NH3)2]2+ adduct undergoes reversible temperature‐induced (T0.5 310 K) and pH‐induced (pKa≈ 4.8) transitions between kinked‐duplex and distorted forms, with the latter forms predominating at high temperature and low pH. A related pH‐induced structural change was observed for the unplatinated duplex (pKa 4.69, Hill coefficient n= 1.4) but was less cooperative than for the platinated duplex (n= 2). The pH‐induced transition is attributed to protonation of cytosine residues and has wider implications, since many reported NMR studies of DNA are carried out near pH 5 to minimize NH‐exchange rates. The [Pt(en)]2+ (where en is 1,2‐ethanediamine) GG chelate of the same duplex is shown to …