PTC52 is similar to ACD1. And it localizes in plastids. It involved in oxidation-reduction process and protein transport. Two Tic55 homologs have been proposed to exist in Arabidopsis: atTic55-II (AT2G24820) and AtPTC52 (AT4G25650) (Protochlorophyllide-dependent Translocon Component, 52 kDa; has also been called atTic55-IV) .