This family represents the N terminal region of the enzyme arginine-tRNA-protein transferase (EC 2.3.2.8), which catalyses the post-translational conjugation of arginine to the N terminus of a protein. In eukaryotes, this functions as part of the N-end rule pathway of protein degradation by conjugating a de-stabilising amino acid to the amino terminal aspartate or glutamate of a protein, targeting the protein for ubiquitin-dependent proteolysis. N terminal cysteine is sometimes modified [1]. In S cerevisiae, Cys20, 23, 94 and/or 95 are thought to be important for activity [2]. Of these, only Cys 94 appears to be completely conserved in this family.

1: Alternative splicing results in differential expression, activity, and localization of the two forms of arginyl-tRNA-protein transferase, a component of the N-end rule pathway. Kwon YT, Kashina AS, Varshavsky A; Mol Cell Biol 1999;19:182-193. PMID:9858543

2: Binding of phenylarsenoxide to Arg-tRNA protein transferase is independent of vicinal thiols. Li J, Pickart CM; Biochemistry 1995;34:15829-15837. PMID:7495814