Binds specific group II introns in chloroplasts and facilitates their splicing. Acts on subgroup IIB introns. The substrates of the subgroup IIB also require the CRM domain proteins CAF1 or CAF2, with a simultaneous binding of CFM3 and CAF1 or CAF2 (PubMed:18799595). May influence the biogenesis of the mitochondrial small ribosomal subunit (By similarity). Interacts with RNA. Part of large ribonucleo-protein particles that contain CAF1 and/or CAF2, and RNC1.