Structural Basis for Stabilization of Z-DNA by Cobalt Hexaammine and Magnesium Cations

Reinhard V. Gessner, Gary J. Quigley, Andrew H.J. Wang, Alexander Rich, Gijs A. van der Marel, Jacques H. van Boom

Research output: Contribution to journalArticlepeer-review

219 Citations (Scopus)


In the equilibrium between B-DNA and Z-DNA in poly(dC-dG), the [Co(NH3)6]3+ ion stabilizes the Z form 4 orders of magnitude more effectively than the Mg2+ ion. The structural basis of this difference is revealed in Z-DNA crystal structures of d(CpGpCpGpCpG) stabilized by either Na+/Mg2+ or Na+/Mg2+ plus [Co(NH3)6]3+. The crystals diffract X-rays to high resolution, and the structures were refined at 1.25 A. The [Co(NH3)6]3+ ion forms five hydrogen bonds onto the surface of Z-DNA, bonding to a guanine O6 and N7 as well as to a phosphate group in the Zn conformation. The Mg2+ ion binds through its hydration shell with up to three hydrogen bonds to guanine N7 and O6. Higher charge, specific fitting of more hydrogen bonds, and a more stable complex all contribute to the great effectiveness of [Co(NH3)6]3+ in stabilizing Z-DNA.

Original languageEnglish
Pages (from-to)237-240
Number of pages4
Issue number2
Publication statusPublished - Jan 1 1985
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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