This family consists of several Cytochrome B6-F complex subunit VI (PetL) proteins found in several plant species. PetL is one of the small subunits which make up The cytochrome b(6)f complex. PetL is strictly required neither for the accumulation nor for the function of cytochrome b6f; in its absence, however, the complex becomes unstable in vivo in aging cells and labile in vitro. It has been suggested that the N-terminus of the protein is likely to lie in the thylakoid lumen [1].

1: Chimeric fusions of subunit IV and PetL in the b6f complex of Chlamydomonas reinhardtii: structural implications and consequences on state transitions. Zito F, Vinh J, Popot JL, Finazzi G; J Biol Chem 2002;277:12446-12455. PMID:11796719