All-atom molecular dynamics simulation of a photosystem i/detergent complex

Area of Science:

• Biophysics
• Structural Biology
• Photosynthesis Research

Background:

• Photosystem I (PSI) is a crucial pigment-protein complex in oxygenic photosynthesis.
• Understanding PSI's structure and dynamics in detergent is vital for its biochemical study.
• Solubilization in detergents like n-dodecyl-β-d-maltoside (DDM) is common but can alter protein behavior.

Purpose of the Study:

• To investigate the solution structure and dynamics of Thermosynechococcus elongatus PSI embedded in a DDM detergent belt.
• To analyze protein-detergent interactions and their impact on PSI stability and function.
• To assess the effect of detergent solubilization on the docking of electron mediators.

Main Methods:

• All-atom molecular dynamics (MD) simulations were performed for 200 ns.
• Root-mean-square deviations (RMSDs) and root-mean-square fluctuations (RMSFs) were calculated to assess stability and mobility.
• Comparisons were made between the PSI-DDM complex and a pure DDM micelle.

Main Results:

• The PSI-DDM complex demonstrated stability throughout the 200 ns simulation.
• High local mobility was observed in solvent-exposed regions and flexible loops.
• The detergent surrounding PSI was less densely packed than in pure micelles, with more ordered tails.
• Structural changes in psaL subunits were noted, contributing to trimeric stability.
• Docking of cytochrome c6 and ferredoxin to PSI was not significantly affected by DDM.

Conclusions:

• MD simulations confirm the stability of PSI within a DDM detergent belt.
• The observed protein-detergent interactions and conformational dynamics are compatible with PSI's function.
• Detergent solubilization does not hinder the interaction of PSI with key electron carriers, validating its use in biochemical studies.