Abstract
PsbZ is a membrane protein of ~6.5 kDa found in Photosystem II (PSII) complexes from cyanobacteria to higher plants. The two helices of PsbZ are located on the perimeter of the dimer near CP43 and PsbK in the cyanobacterial PSII structure. In tobacco and Chlamydomonas reinhardtii, PsbZ is necessary for the stability of the PSII-LHCII super complex and mediates nonphotochemical quenching of chlorophyll fluorescence. However, in cyanobacteria the function is still not clear. In this work, we deleted psbZ gene from Thermosynechococcus elongatus BP-1 and analyzed the function of PsbZ. No difference was observed in the growth under the normal condition and the oxygen evoluving activities in cells, thylakoids, the purified PSII complexes between the wild type and the mutant. Electrophoretic profile of the mutant revealed that PsbZ and PsbK were lost in the purified PSII complexes. It was concluded that PsbZ is important for the stable binding of PsbK.
