tRNA nucleotidyltransferase involved in the synthesis of the tRNA CCA terminus. Adds the terminal adenosine residue to tRNA (PubMed:12370185). Acts as a nucleotidyltransferase and not a poly(A) polymerase (PubMed:12601000). a tRNA with a 3' CC end + ATP = a tRNA with a 3' CCA end + diphosphate Essential, it cannot be deleted. Belongs to the tRNA nucleotidyltransferase/poly(A) polymerase family.