tRNA nucleotidyltransferase involved in the synthesis of the tRNA CCA terminus. In contrast to what is usually observed in eukaryotes for which one enzyme synthesizes the whole tRNA CCA terminus, in S.pombe, cca1 specifically adds two cytidine residues to a tRNA substrate lacking this sequence while cca2 specifically adds the terminal adenosine residue thereby completing the CCA sequence. a tRNA with a 3' CC end + ATP = a tRNA with a 3' CCA end + diphosphate The B/A element (residues 122-124) is present in cca2 but not cca1 and is thought to position tRNA-NCC for terminal A addition. The absence of a C-terminal alpha-helix in cca2 as compared to cca1 might allow for binding of the tRNA-NCC substrate, or prevents binding of the tRNA-N or tRNA-NC substrates. The ERhxxExxxhh motif (residues 234-244) has been suggested to serve to distinguish between A-adding and CC-adding proteins as A-adding enzymes have a small amino acid in the first position while CC-adding enzymes have an E in the first position. Belongs to the tRNA nucleotidyltransferase/poly(A) polymerase family.