This family consists of various Photosystem II (PSII) reaction centre I proteins or PSII 4.8 kDa proteins, PsbI, from the chloroplast genome of many plants and Cyanobacteria. PsbI is a small, integral membrane component of PSII the role of which is not clear [2]. Synechocystis mutants lacking PsbI have 20-30% loss of PSII activity however the PSII complex is not destabilised [2].

1: Isolation and characterization of monomeric and dimeric CP47-reaction center photosystem II complexes. Zheleva D, Sharma J, Panico M, Morris HR, Barber J; J Biol Chem 1998;273:16122-16127. PMID:9632665

2: Directed inactivation of the psbI gene does not affect photosystem II in the cyanobacterium Synechocystis sp. PCC 6803. Ikeuchi M, Shukla VK, Pakrasi HB, Inoue Y; Mol Gen Genet 1995;249:622-628. PMID:8544827