Abstract
Crystal structural model of photosystem II (PS II) revealed the presence of an unknown low molecular weight transmembrane polypeptide in PS II core complexes from Thermosynechococcus elongatus. We analyzed precisely the polypeptide composition of PS II complexes purified from T. elongatus and found one Ycf protein as a PS II component. To confirm the association of this protein in other cyanobacterial PS II complexes, and to investigate the function of it in PS II, we deleted the corresponding gene in Synechocystis 6803.
The mutant cells grew and evolved oxygen at almost the same rate as wild type. However, the oxygen-evolving activity in the purified mutant PS II complexes diminished compared to that in the wild-type PSII complexes. Analysis of polypeptide profile revealed a partial release of extrinsic proteins in the purified mutant PS II complexes. These results indicate that this protein is a structural component in PS II complexes.
