Required for the splicing of group IIA introns in chloroplasts, and especially for atpF, by regulating the intron folding. Forms splicing particles with RNA. Also involved in chloroplast protein translation. Optimum pH is 7-7.5. Optimum temperature is 25-30 degrees Celsius. Homodimer. Interacts with RNA, specifically with atpF intron. Part of large ribonucleo-protein complexes that include group IIA introns and CRS1. A number of isoforms are produced. According to EST sequences. More expressed in leaves than in roots.