Electron microscopy in structural studies of Photosystem II

Area of Science:

• Biochemistry
• Structural Biology
• Microscopy

Background:

• Photosystem II (PS II) is a crucial pigment-protein complex in photosynthesis.
• Understanding its structure is key to comprehending light energy conversion.

Purpose of the Study:

• To review structural information of Photosystem II (PS II).
• To summarize its arrangement and interactions with antenna proteins in thylakoid membranes.
• To compare EM-derived data with X-ray crystallography findings.

Main Methods:

• Electron microscopy (EM) techniques including ultrathin sectioning, freeze-fracturing, freeze-etching, and negative staining.
• Cryo-electron crystallography of two-dimensional crystals.
• X-ray crystallography of cyanobacterial PS II.

Main Results:

• EM provides low and high-resolution structural insights into PS II.
• Detailed information on subunit organization, particularly oxygen-evolving complex (OEC) proteins, is obtained.
• Comparison with X-ray crystallography data offers a comprehensive structural understanding.

Conclusions:

• Electron microscopy is a powerful tool for elucidating PS II structure and organization.
• The review consolidates EM-based structural data of PS II in higher plants and cyanobacteria.
• Integration of EM and X-ray crystallography enhances structural resolution and subunit analysis.