Required for the insertion of some light harvesting chlorophyll-binding proteins (LHCP) into the chloroplast thylakoid membrane. Required for the insertion of LHCB1, LHCB4.1 and LHCB5 proteins into thylakoid membrane, while it is not required for insertion of proteins PsbX, PsbW and PsbY. Homodimer. Forms a complex with CPFTSY and the signal recognition particle (cpSRP). Interacts (via C-terminus) with CAO/cpSRP43 (via chromodomains 2 and 3) and with LHCP. Interacts with PAM68, SECE1 and SCY1 (PubMed:12217076, PubMed:14517205, PubMed:15988575, PubMed:17513500, PubMed:20018841, PubMed:20828566, PubMed:20923938, PubMed:21832051). Interacts with TERC (PubMed:24612058). Interacts with ALB4 (PubMed:26265777). Interacts with STIC2 (PubMed:28684427). Mainly expressed in organs that contain green tissues such as leaves, flower buds and stems. The C-terminus (339-462) is required for interaction with cpSRP. Belongs to the OXA1/ALB3/YidC (TC 2.A.9.2) family. Two articles reported an interaction with LPA2; however, these papers were later retracted.