|Chloroplast light-harvesting complex II holds half of the chlorophyll in nature, and therefore harvests half of the sunlight that is converted in photosynthesis. This pigment-protein complex is embedded in the chloroplast thylakoid membrane. The graphic, drawn by Dr Per-Ola Arvidsson, shows a view of a single polypeptide chain of the protein part of the complex, viewed parallel to the membrane plane. The helices are based on the structure of Kuehlbrandt et al., while the loops are schematic.
From the amino-terminal end of the polypeptide, at the top of the picture, the polypeptide chain passes through the membrane as a long helix, represented by a cylinder. The chain passes back through the membrane as a shorter helix, then back again as a third, long helix. A fourth, short helix runs along the inner surface of the membrane.
The amino-terminus, exposed to the outer surface of the membrane, contains the site of phosphorylation. We have shown that phosphorylation regulates the function of the complex by altering its structure. Kinemages of the light-harvesting complex and of the phosphorylated amino-terminus are available. An animation of a possible structure at the amino-terminus of the phosphorylated protein is also presented with its atomic coordinates.
This page with a QuickTime animation (1.2 MB) in place of the graphic.
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