This family consists of various prokaryotic SecD and SecF protein export membrane proteins. This SecD and SecF proteins are part of the multimeric protein export complex comprising SecA, D, E, F, G, Y, and YajC [1]. SecD and SecF are required to maintain a proton motive force [2].

1: SecDF of Bacillus subtilis, a molecular Siamese twin required for the efficient secretion of proteins. Bolhuis A, Broekhuizen CP, Sorokin A, van Roosmalen ML, Venema G, Bron S, Quax WJ, van Dijl JM; J Biol Chem 1998;273:21217-21224. PMID:9694879

2: SecD and SecF are required for the proton electrochemical gradient stimulation of preprotein translocation. Arkowitz RA, Wickner W; EMBO J 1994;13:954-963. PMID:8112309