Functional Analysis of PsbY and PsbZ Proteins in Photosystem II from the Thermophilic Cyanobacterium Thermosynechococcus elongatus BP-1.

Abstract

PsbY and PsbZ are the membrane proteins of ~5.0 kDa and ~6.5 kDa in Photosystem II (PSII) complexes. We deleted psbY and psbZ genes from Thermosynechococcus elongatus BP-1.
The oxygen-evolving activity in ΔpsbZ PSII complexes was lower than that in the wild-type PSII complexes. Most of Ycf12 as well as PsbK was lost in ΔpsbZ PSII complexes. These suggest that PsbZ is important for the stable binding of PsbK and Ycf12 with PSII core intrinsic proteins. We analyzed quantity of Mn from those PSII complexes.
No difference was observed in the growth under the several conditions between the wild-type and ΔpsbY. the oxygen-evolving activity of ΔpsbY PSII complexes were 20-30% lower than those of the wild-type. BN-PAGE revealed that the dimeric PSII was no significant reduced in ΔpsbY. Electrophoretic profile and analysis of the crystal structure revealed that PsbY was disappeared and no release of the extrinsic proteins was observed.