Deaminates adenosines to inosines in tRNA-Arg(ACG). Exclusively involved in A-to-I editing of the prokaryote-type chloroplast-tRNA and not involved in C-to-U editing. adenosine(34) in tRNA + H(+) + H2O = inosine(34) in tRNA + NH4(+) Binds 1 zinc ion per subunit. Homodimer. The C-terminus (843-1307) is sufficient for the deamination. Loss of cp-tRNA editing, decreased chloroplast translation and impaired photosynthesis. Since the absence of A-to-I editing is compatible with plant survival, a limitted two out of three codon recognition occurs in chloroplasts, though this mechanism is less efficient than wobble pairing. Belongs to the cytidine and deoxycytidylate deaminase family.