1H and 31P nuclear magnetic resonance studies of spermine binding to the Z-DNA form of d(m5CGm5CGm5CG)2. Evidence for decreased spermine mobility

Debra L. Banville, Burt G. Feuerstein, Richard H. Shafer

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The binding of spermine to the d(m5CGm5CGm5CG) duplex has been studied by proton and phosphorus nuclear magnetic resonance techniques in order to investigate the mobility and nature of spermine bound to the resulting Z-DNA complex. A characterization of the B to Z transition as a function of increasing spermine concentration demonstrated doubling of the non-exchangeable proton and the phosphorus peaks at a ratio of about 1:1 (spermine/duplex) and a re-simplification of the spectrum at 2:1 (spermine/duplex) where about 90% or the DNA was fully converted into the Z-form. However, some of the Z-DNA proton chemical shifts differed between the 1:1 and 2:1 titration points. Since these differences involved primarily the exchangeable terminal imino and amino protons, they could result from end effects. Discrepancies were generally not observed with the non-terminal proton shifts nor with the phosphorus shifts. These proton and phosphorus chemical shift changes are fully consistent with a, B to Z transition. Complexed spermine peaks appear about 0.1 parts per million upfield from the uncomplexed form. The spermine and both the B and Z-DNA hexamer signals are noticeably broadened at the 1:1 ratio but the remaining signals re-sharpen at the 2:1 ratio. Both one-dimensional and two-dimensional studies revealed negative nuclear Overhauser effect (NOE) contacts between each spermine proton. Therefore, spermine has a longer correlation time than that observed for unbounded spermine. These results are contrasted with the positive NOE contacts observed for the B-DNA-spermine complexes reported by Wemmer et al. using the dodecamer d(CGCGAATTCGCG)2 and reported here using the hexamer d(ATGCAT)2. While the mobility of spermine in the Z-DNA complex is significantly less than that of the B-DNA complex, no clear evidence of intermolecular spermine-DNA proton NOE contacts is observed.

Original languageEnglish (US)
Pages (from-to)585-590
Number of pages6
JournalJournal of Molecular Biology
Volume219
Issue number4
DOIs
StatePublished - Jun 20 1991

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Keywords

  • B-DNA
  • Z-DNA
  • negative NOE contacts
  • proton n.m.r.
  • spermine mobility

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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