Abstract
Several factors required for the assembly of photosystem I (PSI) complex have been reported so far. Ycf3 and Ycf4 proteins are essential for an early stage of the assembly process while RubA and HCF101 proteins are involved in the integration of 4Fe-4S clusters. The chloroplast-encoded Ycf4 is a part of a large complex, which transiently binds PSI proteins to assist the assembly of PSI complex. The Ycf4 complex was purified from the thylakoid extracts of Chlamydomonas wild-type cells and was estimated to be more than 1000kDa. Of interest is that this large complex contains PSI proteins. Ycf4 complex was also purified by affinity chromatography from the thylakoid extracts containing Ycf4 fused with TAP tag. We will discuss the subunit composition and cofactors of the purified Ycf4 complex and a possible function in the assembly of PSI complex.
