Abstract
The photosystem 1 (PS1) complex of the green alga Chlamydomonas reinhardtii contains fourteen subunits (PsaA-L, PsaN-O) and nine light-harvesting chlorophyll a/b complex (LHCI). In contrast to plant PSI complexes, Chlamydomonas PS1 complex looses some peripheral subunits during solubilization and/or purification. In order to purify PS1 complexes with more intact structure, it is necessary to develop a mild purification procedure. Here we report our recent development of a rapid and efficient purification method that uses glycerol gradient ultracentrifugation. This method separates photosystems 1 and 2 more perfectly than sucrose density gradient ultracentrifugation and need shorter time for centrifugation. The resulting preparation contained 12 photosystem 1 subunits and nine LHCI subunits but lost PsaO and PsaN. The subsequent purification by ion exchange chromatography removed PsaH as well as small contaminations, indicating the association of PsaH with photosystem 1 core complex is not stable. The compositions of lipids in the purified preparation will also be reported.
