Evaluating the stoichiometry of macromolecular complexes using multisignal sedimentation velocity

Area of Science:

• Biochemistry
• Molecular Biology
• Analytical Chemistry

Background:

• Understanding macromolecular complex composition is vital for molecular physiology.
• Stoichiometry determination is a key challenge in analyzing macromolecular complexes.
• Analytical ultracentrifugation provides hydrodynamic information but often requires complementary methods for stoichiometry.

Purpose of the Study:

• To detail and validate a multisignal sedimentation velocity (MSSV) method for determining macromolecular complex stoichiometry.
• To establish criteria for spectral resolution of cosedimenting species in MSSV experiments.
• To explore the application of MSSV for deriving equilibrium association constants.

Main Methods:

• Simultaneous collection of concentration profile data using multiple detection signals (e.g., Rayleigh interferometry, UV spectrophotometry).
• Analysis of sedimentation velocity (SV) data to generate continuous sedimentation-coefficient distributions for spectrally distinguishable components.
• Integration of hydrodynamic data with spectral information to derive molar ratios and stoichiometry.

Main Results:

• Development of a predictive test for spectral resolvability of macromolecules in MSSV experiments.
• Introduction of graphical tools for experimental design and assessment of spectral discrimination success.
• Demonstration of accurate stoichiometry determination for macromolecular complexes using MSSV.

Conclusions:

• Multisignal sedimentation velocity (MSSV) is a powerful technique for elucidating macromolecular complex stoichiometry.
• MSSV enables the calculation of molar ratios by spectrally resolving cosedimenting components.
• The method holds potential for characterizing complex formation and stability through equilibrium association constant determination.