This entry represents the C-terminal of PsbP/CyanoP and PsbP-like proteins (also known as 23 kDa subunit of oxygen evolving system of photosystem II) from plants and Cyanobacteria. The 23 KDa PsbP protein is required for PSII to be fully operational in vivo, it increases the affinity of the water oxidation site for Cl- and provides the conditions required for high affinity binding of Ca2+ [2]. Structure of CyanoP from Synechocystis sp. revealed that it has an alpha-beta-alpha fold containing 10 beta strands organized into two anti-parallel beta-sheets, packed against two alpha-helices. This entry covers the last three beta-stands (beta8-beta9-beta10) and the C-terminal alpha-helix [1,2].

1: Solution structure of CyanoP from Synechocystis sp. PCC 6803: new insights on the structural basis for functional specialization amongst PsbP family proteins. Jackson SA, Hinds MG, Eaton-Rye JJ; Biochim Biophys Acta. 2012;1817:1331-1338. PMID:22414666

2: Structure of CyanoP at 2.8 A: implications for the evolution and function of the PsbP subunit of photosystem II . Michoux F, Takasaka K, Boehm M, Nixon PJ, Murray JW; Biochemistry. 2010;49:7411-7413. PMID:20698571