Biochemical and structural studies of the large Ycf4-photosystem I assembly complex of the green alga Chlamydomonas reinhardtii.

摘要: Ycf4 is a thylakoid protein essential for the accumulation of photosystem I (PSI) in Chlamydomonas reinhardtii. Here, tandem affinity purification tagged was used to purify stable Ycf4-containing complex >1500 kD. This also contained opsin-related COP2 and PSI subunits PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, as identified by mass spectrometry (liquid chromatography-tandem spectrometry) immunoblotting. Almost all wild-type cells copurified sucrose gradient ultracentrifugation subsequent ion exchange column chromatography, indicating intimate exclusive association COP2. Electron microscopy revealed that largest structures purified preparation measure 285 x 185 A; these particles may represent several large oligomeric states. Pulse-chase labeling polypeptides associated with are newly synthesized partially assembled pigment-containing subcomplex. These results indicate act scaffold assembly. A decrease 10% levels RNA interference increased salt sensitivity stability but did not affect PSI, suggesting