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Role of Mg++ in the mithramycin-DNA interaction: evidence for two types of mithramycin-Mg++ complex

P Aich1, D Dasgupta

  • 1Crystallography & Molecular Biology Division, Saha Institute of Nuclear Physics, Calcutta, India.

Biochemical and Biophysical Research Communications
|December 14, 1990
PubMed

Insights

Mithramycin (MTR) forms two distinct complexes with magnesium ions (Mg++), influencing its DNA binding. Understanding these Mg++ complexes is key to the molecular basis of MTR-DNA interactions.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Spectroscopy

Background:

  • Mithramycin (MTR) and Chromomycin A3 are antitumor antibiotics.
  • They inhibit DNA-dependent RNA polymerase by interacting with DNA in the presence of divalent metal ions like Mg++.

Purpose of the Study:

  • To investigate the role of Mg++ in the DNA binding of MTR.
  • To characterize the interaction between MTR and Mg++.

Main Methods:

  • Absorbance spectroscopy was used to study MTR-Mg++ binding.
  • Circular Dichroism (CD) spectroscopy was employed to analyze MTR-Mg++ complexes.

Main Results:

  • MTR binds to Mg++ independently.
  • Two distinct MTR-Mg++ complexes (Complex I and Complex II) are formed at different Mg++ to MTR concentration ratios.
  • These complexes are predicted to bind DNA with varying affinities and rates.

Conclusions:

  • The relative concentration of Mg++ is crucial for understanding MTR-DNA interactions.
  • Two MTR-Mg++ complexes exhibit differential DNA binding properties.

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