Oxygen evolving membranes and particles from the transformable cyanobacterium Synechocystis sp. PCC6803

Area of Science:

• * Photosynthesis research
• * Molecular biology
• * Cyanobacterial studies

Background:

• * Photosystem II (PS II) is central to oxygenic photosynthesis.
• * Isolating functional PS II is key to studying its mechanism.
• * Synechocystis sp. PCC6803 is a model organism for cyanobacterial research.

Purpose of the Study:

• * To isolate and characterize Photosystem II (PS II) particles from Synechocystis sp. PCC6803.
• * To assess the oxygen-evolving activity of isolated PS II.
• * To confirm the purity and integrity of the isolated PS II fraction.

Main Methods:

• * Isolation of membranes from Synechocystis sp. PCC6803 grown under red light.
• * Detergent extraction of membranes using octylglucoside and dodecylmaltoside.
• * DEAE column chromatography for purification of PS II particles.
• * Characterization using oxygen evolution assays, fluorescence spectroscopy, and immunoblotting.

Main Results:

• * Isolated membranes showed high oxygen evolution rates (500-700 μmole O2/mg chl/h).
• * Purified PS II particles exhibited even higher oxygen evolution rates (>1000 μmole O2/mg chl/h).
• * PS II particles showed characteristic fluorescence emission (685 and 696 nm) and cross-reactivity with spinach PS II core polypeptides, lacking phycobilin signals.

Conclusions:

• * Functional Photosystem II (PS II) particles can be effectively isolated from Synechocystis sp. PCC6803.
• * The isolation procedure yields highly active PS II with preserved core reaction center components.
• * This provides a valuable system for detailed mechanistic studies of cyanobacterial photosynthesis.