YCF48 is one of several assembly factors of the photosynthesis system II. The photosynthesis system II occurs in Cyanobacteria that are Gram-negative bacteria performing oxygenic photosynthesis. One of the three membranes surrounding these bacteria is the inner thylakoid membrane (TM) system that is localised within the cell and houses the large pigment-protein complexes of the photosynthetic electron transfer chain, i.e. Photosystem (PS) II, PSI, the cytochrome b6f complex, and the ATP synthase. YCF48 is necessary for efficient assembly and repair of the PSII [1]. YCF48 is found predominantly in the thykaloid membrane [2]. It is a BNR repeat protein.

1: The cyanobacterial homologue of HCF136/YCF48 is a component of an early photosystem II assembly complex and is important for both the efficient assembly and repair of photosystem II in Synechocystis sp. PCC 6803. Komenda J, Nickelsen J, Tichy M, Prasil O, Eichacker LA, Nixon PJ; J Biol Chem. 2008;283:22390-22399. PMID:18550538

2: An intermediate membrane subfraction in cyanobacteria is involved in an assembly network for Photosystem II biogenesis. Rengstl B, Oster U, Stengel A, Nickelsen J; J Biol Chem. 2011;286:21944-21951. PMID:21531723