This family consists of hypothetical Ycf4 proteins from various chloroplast genomes. It has been suggested that Ycf4 is involved in the assembly and/or stability of the photosystem I complex in chloroplasts [1].

1: The chloroplast ycf3 and ycf4 open reading frames of Chlamydomonas reinhardtii are required for the accumulation of the photosystem I complex. Boudreau E, Takahashi Y, Lemieux C, Turmel M, Rochaix JD; EMBO J 1997;16:6095-6104. PMID:9321389