Catalyzes the addition and repair of the essential 3'-terminal CCA sequence in tRNAs without using a nucleic acid template. Adds these three nucleotides in the order of C, C, and A to the tRNA nucleotide-73, using CTP and ATP as substrates and producing inorganic pyrophosphate. a tRNA precursor + ATP + 2 CTP = a tRNA with a 3' CCA end + 3 diphosphate Homodimer. The crystal structure reveals a seahorse-shaped subunit consisting of four domains: head, neck, body, and tail. The head domain contains the nucleotidyltransferase activity. The neck domain provides a specific template for the incoming ATP or CTP, whereas the body and tail domains may be involved in tRNA binding. A single active site specifically recognizes both ATP and CTP and is responsible for their addition. Belongs to the tRNA nucleotidyltransferase/poly(A) polymerase family. Bacterial CCA-adding enzyme type 3 subfamily.