With S4 and S5 plays an important role in translational accuracy. Located at the interface of the 30S and 50S subunits (By similarity). Part of the 30S ribosomal subunit. Belongs to the universal ribosomal protein uS12 family. There is 1 gene for this protein in each of the chloroplast inverted repeats; while they are usually identical, in this organism they are not. The other copy is AC A4QJV5.