A major RuBisCO chaperone. Acts after GroEL-GroES chaperonin to fold and/or assemble the large subunit of RuBisCO (ccbL, rbcL). Cooperates with RbcX in RbcL folding, plays the major role in assembly of dimers into RbcL(8)-Raf1(8) intermediate complexes. RbcS replaces Raf1, leading to holoenzyme formation. Required for optimal reconstitution of RuBisCO upon expression of rbcL-rbcS subunits in E.coli. Only interacts with the large subunit (cbbL, rbcL). Probably acts in the final stages of RuBisCO assembly, possibly participating in the addition of the small subunit (ccbS, rbcS). Homodimer. Forms an RbcL(8)-Raf1(8) complex. Forms complexes of many stoichiometries with RbcL with and without RbcS. RbcX and Raf1 can bind simultaneously to RbcL. Interacts with the large subunit of RuBisCO in the cytoplasm. Has 3 domains, the N-terminal alpha-helical domain, an extended flexible linker and the C-terminal beta-sheet domain. The 2 C-terminal beta-sheet domains are swapped and pack against each other to form the dimer interface. Belongs to the RAF family.