This domain is found at the C-terminal end of T4 RNA ligase 1 (Rnl1) from Bacteriophage T4 and similar proteins from tailed bacteriophages. Rnl1 is involved in countering a host defense mechanism by repairing tRNA. The C-terminal domain shows an all alpha-helical fold and has a charge distribution and architecture for helix-nucleic acid groove interaction compatible with tRNA binding. It confers specificity for the repair of tRNAs with breaks in the anticodon loop [1,2].

1: Molecular architecture and ligand recognition determinants for T4 RNA ligase. El Omari K, Ren J, Bird LE, Bona MK, Klarmann G, LeGrice SF, Stammers DK; J Biol Chem. 2006;281:1573-1579. PMID:16263720

2: Two-metal versus one-metal mechanisms of lysine adenylylation by ATP-dependent and NAD(+)-dependent polynucleotide ligases. Unciuleac MC, Goldgur Y, Shuman S; Proc Natl Acad Sci U S A. 2017;114:2592-2597. PMID:28223499