Models of mobility-shift assay of complexes between dimerizing protein and DNA

Area of Science:

• Biochemistry
• Molecular Biology
• Physical Chemistry

Background:

• Electrophoretic mobility-shift assays (EMSA) are crucial for studying protein-DNA interactions.
• Understanding macromolecular interactions, especially protein dimerization, is key to interpreting binding data.
• Kinetic and transport phenomena can influence observed binding patterns in assays.

Purpose of the Study:

• To develop and validate theoretical models for electrophoretic mobility-shift assays (EMSA) involving dimerizing proteins and DNA.
• To investigate the impact of simultaneous dimerization and DNA-binding reactions on assay outcomes.
• To establish methods for accurately determining equilibrium binding constants from EMSA data.

Main Methods:

• Application of mass action theory to simultaneous dimerization and DNA-binding reactions.
• Numerical solution of transport-reaction equations for four distinct models.
• Analysis of theoretical mobility-shift patterns across varying protein concentrations.
• Extrapolation techniques to derive equilibrium constants from apparent binding constants.

Main Results:

• Theoretical mobility-shift patterns were generated for different models of protein-DNA complex formation.
• Apparent binding constants were obtained, which, upon extrapolation, yield estimates of equilibrium constants.
• A method was identified for extracting equilibrium binding constants from dimer-binding data, requiring independent determination of dimerization constants.
• Protein dimerization occurring after DNA binding simplifies the extrapolation process.

Conclusions:

• The developed models provide a theoretical framework for interpreting EMSA data involving dimerizing proteins.
• Accurate determination of equilibrium binding constants is achievable through careful analysis and extrapolation.
• Independent measurement of dimerization constants is essential for precise quantification of binding affinities.
• The study highlights distinct behaviors of protein dimerization on and off DNA.