Ycf54 is found encoded in the chloroplast genomes of algae, also found in plants and cyanobacteria. It is a component of the MgPME-cyclase complex and plays two roles: first, it plays a critical role in the assembly/stability of the Mg-cyclase complex and its constituents; secondly, it is required for normal Pchlide formation [1,2]. This protein is required for optimal MgPME-cyclase activity, although it is not absolutely essential.

1: The Chlamydomonas genome reveals the evolution of key animal and plant functions. Merchant SS, Prochnik SE, Vallon O, Harris EH, Karpowicz SJ, Witman GB, Terry A, Salamov A, Fritz-Laylin LK, Marechal-Drouard L, Marshall WF, Qu LH, Nelson DR, Sanderfoot AA, Spalding MH, Kapitonov VV, Ren Q, Ferris P, Lindquist E, Shapiro H, Lucas SM, Gr Science. 2007;318:245-250. PMID:17932292

2: Conserved residues in Ycf54 are required for protochlorophyllide formation in Synechocystis sp. PCC 6803. Hollingshead S, Bliss S, Baker PJ, Neil Hunter C; Biochem J. 2017;474:667-681. PMID:28008132