Model of subcomplex I and II involved in psaA trans-splicing. Comparative TAP analyses revealed that subcomplex I comprises at least ten core subunits. Five of these were previously characterized as splicing factors, namely Raa1, Raa3, Raa4, Raa8, and Rat2. Subcomplex I is an RNP and copurifies with psaA exon 1 precursor and tscA RNA [123]. Subcomplex II participates in the second psaA splicing reaction and comprises at least seven subunits [143]. These were identified by TAP technology, using Raa2 and Raa7 as baits. Copurification of psaA exon 2 and exon 3 precursors indicate that the membrane-associated (thylakoid membrane at the top) subcomplex II is able to form an RNP. Bait proteins used in this study for TAP are denoted with an anchor. Proteins involved in both psaA splicing reactions are highlighted in yellow, psaA-i1 splicing factors are colored in red, and psaA-i2 splicing factors are colored in orange. Uncharacterized proteins are denoted by their molecular mass in kDa. Subcomplex I: 71 kDa = Cre17.g724450; 109 kDa = Cre12.g533351; 109 kDa OPR = Cre01.g001501; 113 kDa = Cre08.g373878; 139 kDa = Cre11.g467652. Subcomplex II: 52 kDa = Cre03.g179000; 58 kDa = Cre17.g728850; 67 kDa = Cre02.g073200 (OPR, octatricopeptide repeat).