This domain is the N-terminal domain from the enzyme (EC:2.4.2.-) which modifies exclusively the initiator tRNA in position 64 using 5'-phosphoribosyl-1'-pyrophosphate as the modification donor. As the initiator tRNA participates both in the initiation and elongation of translation, the 2'-O-ribosyl phosphate modification discriminates the initiator tRNAs from the elongator tRNAs [1]. The N-terminal domain is the most conserved region of the protein [2].

1: Rit1, a tRNA backbone-modifying enzyme that mediates initiator and elongator tRNA discrimination. Astrom SU, Bystrom AS; Cell 1994;79:535-546. PMID:7954819

2: Identification and modeling of a phosphatase-like domain in a tRNA 2'-O-ribosyl phosphate transferase Rit1p. Czerwoniec A, Bujnicki JM; Cell Cycle. 2011;10:3566-3570. PMID:22030622