Comparison between the influences of phosphatidylcholine and Triton X-100 on the protein secondary structures and oxygen-evolving activity of photosystem II

The structural and functional alterations within the PSII membrane from phosphatidylcholine reconstitution and Triton X-100 (TX-100) treatment were studied by using Fourier transform-infrared (FT-IR) spectroscopic technique and oxygen electrode. Phosphatidylcholine reconstitution showed no significant effect on the protein secondary structures of PS II membrane but an increase of the rate of PS II -mediated oxygen-evolution. The phosphatidylcholine lipids with different length of acyl chains displayed different capabilities to stimulate oxygen-evolution. In contrast, perturbation of the bilayer lipids by TX-100 resulted in obvious changes of the protein secondary structures within the PSII membrane and in the loss of the PS II -mediated oxygen-evolving activity. The results indicate the importance of membrane integrity in maintaining the stability of the photosynthetic membrane proteins.