Lattice Models for Protein Organization throughout Thylakoid Membrane Stacks

Area of Science:

• Photosynthesis research
• Membrane biophysics
• Computational biology

Background:

• Proteins in photosynthetic membranes can self-organize into patterned arrays.
• Interactions between proteins in stacked membrane layers influence this ordering.
• Thylakoid membrane architecture presents both attractive and repulsive forces affecting protein arrangement.

Purpose of the Study:

• To investigate the interplay of opposing forces in protein organization within stacked thylakoid membranes.
• To explore phase transitions in the periodic geometry of thylakoid membrane disks.
• To model the factors influencing protein density and arrangement.

Main Methods:

• Development of a lattice model for protein interactions.
• Inclusion of intra-layer and inter-layer protein attractions.
• Modeling of steric repulsion and protein density regulation via stromal exchange.
• Application of mean-field analysis and computer simulations.

Main Results:

• The model predicts rich phase behavior, including a broken-symmetry striped phase.
• This striped phase is sensitive to chemical potential, disrupted at extremes.
• Protein arrangement is significantly influenced by the mesoscale vertical structure of thylakoids.

Conclusions:

• Opposing forces within thylakoid membranes lead to complex protein organization.
• The discovered striped phase and its sensitivity suggest a mechanism for regulating photosynthetic function.
• Microscopic protein arrangement is tunable by the macroscopic thylakoid structure.