This domain is predominantly found at the N-terminal end of proteins from cyanobacteria and plants, including Biogenesis factor required for ATP synthase 1 (BFA1, Swiss:F4J1U2) from Arabidopsis thaliana. BFA1 promotes the assembly of the CF1 subcomplex of the chloroplast ATP synthase by specifically interacting with the gamma and beta subunits. This domain consists of nine beta-sheets and two alpha- helices forming an atypical beta-barrel, which locates perpendicularly to the typical beta-barrel formed by the C-terminal domain [1].

1: Nucleus-Encoded Protein BFA1 Promotes Efficient Assembly of the Chloroplast ATP Synthase Coupling Factor 1. Zhang L, Pu H, Duan Z, Li Y, Liu B, Zhang Q, Li W, Rochaix JD, Liu L, Peng L; Plant Cell. 2018;30:1770-1788. PMID:30012777