Abstract
Although structure and function of PSI complex have been intensively investigated, the molecular mechanism for synthesis of PSI complex still remains elusive. It has been revealed that the chloroplast-encoded Ycf4 is essential for assembly of PSI complex in the green alga Chlamydomonas reinhardtii. We have already reported that Ycf4 is a component of the large complex of 1800 kDa and this complex can be purified with two-step affinity chromatography by fusion of Ycf4 with TAP (tandem affinity purification) tag. In the present study, we improved the purification by fractionation of Ycf4-enriched fraction with DEAE ion exchange chromatography before the affinity purification. The partially purified Ycf4-complex was subjected to the two-step affinity chromatography. The resulting Ycf4-complex contained 14 subunits from 15 to 68 kDa in addition to 28 kDa Ycf4. This result that the Ycf4-complex contains a number of subunits is consistent with its large size.
