ABSTRACT
This chapter discusses the structural, enzymological, functional, and regulatory aspects of transfer RNA (tRNA) nucleotidyltransferase. The transfer RNA (tRNA) nucleotidyltransferases display an interesting range of specificities with respect to their nucleoside triphosphate and nucleic acid substrates. The absence of nucleotides in homogeneous preparations of tRNA nucleotidyltransferase precludes the possibility that accurate synthesis of the -C-C-A sequence is dependent on a nucleic acid template. tRNA molecules are relatively stable in vivo, and if any 3’ exonucleolytic cleavage does occur it is immediately repaired by tRNA nucleotidyltransferase. The 3’ terminal trinucleotide sequence, -C-C-A, is present on all tRNA molecules and is required for the acceptor and transfer functions of this nucleic acid. The increase in defective tRNA could be due to increased removal of terminal nucleotides by elevated nuclease activity or higher levels of uncharged tRNA. Alternatively, some other component of the synthesizing system could be limiting.
