Nano-mechanical mapping of the interactions between surface-bound RC-LH1-PufX core complexes and cytochrome c 2...

Area of Science:

• Photosynthesis research
• Biophysics
• Molecular biology

Background:

• Photosynthesis involves electron transfer between membrane-bound complexes and extrinsic partners.
• Understanding these interactions is crucial for mapping protein locations in photosynthetic membranes.

Purpose of the Study:

• To map the location of surface-attached reaction centre-light-harvesting 1-PufX (RC-LH1-PufX) complexes.
• To utilize the specific electron transfer interaction between RC-LH1-PufX and cytochrome c 2 (cyt c 2) for nano-mechanical mapping.

Main Methods:

• Atomic force microscopy (AFM) was employed with an AFM probe functionalized with cyt c 2.
• Single-molecule force spectroscopy was used to quantify interaction forces under native conditions.
• Adhesion and topographic imaging were combined to spatially locate proteins.

Main Results:

• The mean interaction force between photo-oxidized RC-His12-LH1-PufX and cyt c 2 was approximately 480 pN with a 66% interaction frequency.
• This interaction frequency decreased 5.5-fold when electron transfer was abolished (chemically reduced complexes in the dark).
• Affinity-based AFM methods proved useful for locating proteins where topology alone was insufficient.

Conclusions:

• Specific molecular interactions can be leveraged for high-resolution protein localization on membranes.
• AFM-based nano-mechanical mapping provides a powerful tool for studying protein interactions in photosynthetic systems.
• This technique enhances our ability to understand the spatial organization of photosynthetic complexes.