Required for assembly or stability of RuBisCO. Acts at a postchaperonin step to fold and/or assemble the large subunit (rbcL) into RuBisCO. RAF1 binds first to a rbcL dimer (rbcL(2)), leading to a rbcL(8)-RAF1(4) complex formation. In the next step, RBCS displaces RAF1, thus resulting in holoenzyme formation. Homodimer. Has 3 domains, the N-terminal alpha-helical domain, an extended flexible linker and the C-terminal beta-sheet domain. The N-terminal alpha-helical domain stabilizes RbcL dimers and RbcL dimer-dimer interactions, facilitating RbcL(8) formation. The C-terminal beta-sheet domain probably dimerizes Raf1 (PubMed:26237510). The 2 C-terminal beta-sheet domains are swapped and pack against each other to form the dimer interface (By similarity). Belongs to the RAF family.