This family consists of several photosystem II 12 kDa extrinsicprotein (PsbU) proteins from cyanobacteria and algae. PsbU is anextrinsic protein of the photosystem II complex of cyanobacteriaand red algae. PsbU is known to stabilise the oxygen-evolvingmachinery of the photosystem II complex against heat-inducedinactivation [1]. Photosystem II 12 kDa extrinsic protein (PsbU) PsbU