Increases the formation of ribosomal termination complexes and stimulates activities of RF-1 and RF-2. It binds guanine nucleotides and has strong preference for UGA stop codons. It may interact directly with the ribosome. The stimulation of RF-1 and RF-2 is significantly reduced by GTP and GDP, but not by GMP (By similarity). Belongs to the TRAFAC class translation factor GTPase superfamily. Classic translation factor GTPase family. PrfC subfamily.