Probably participates in efficiency of electron transfer from plastocyanin to P700 (or cytochrome c553 in algae and cyanobacteria). This plastocyanin-docking protein contributes to the specific association of plastocyanin with PSI. The G.violaceus PSI reaction center is composed of one copy each of PsaA,B,C,D,E,F,L,M and Z, and forms trimeric complexes. The soluble domain is associated with the lumenal side of the cytoplasmic membrane. Belongs to the PsaF family.