Molecular dynamics study on the interaction of a mithramycin dimer with a decanucleotide duplex

Area of Science:

• Structural Biology
• Computational Chemistry
• Molecular Biophysics

Background:

• Mithramycin (MTR) is a minor groove binding drug.
• MTR forms dimer complexes ((MTR)2Mg2+) with magnesium ions.
• NMR structures provide a basis for understanding MTR-DNA interactions.

Purpose of the Study:

• To investigate the complex of mithramycin (MTR) and a DNA duplex using molecular dynamics (MD) simulations.
• To determine the binding free energy and structural changes upon MTR dimer binding to DNA.
• To analyze the contributions of different energy types to the binding process.

Main Methods:

• Molecular dynamics (MD) simulations using AMBER 7.0.
• Utilized NMR solution structure of a 2:1 duplex complex as the starting point.
• Calculated partial atomic charges using multiple-RESP fitting and adapted force field parameters.

Main Results:

• The first (MTR)2Mg2+ complex binding (1:1 complex) did not significantly stiffen the DNA duplex.
• Binding of a second (MTR)2Mg2+ complex (2:1 complex) substantially reduced the overall DNA duplex flexibility.
• Van der Waals interactions were dominant, leading to inward pointing sugar residues and a widened minor groove.

Conclusions:

• The extent of DNA flexibility reduction depends on the number of bound MTR dimer complexes.
• MTR dimer binding induces significant structural alterations in the DNA minor groove.
• MD simulations provide valuable insights into the molecular mechanisms of MTR-DNA interactions.