Ubiquitin-related modifier 1 (Urm1)

Acts as a sulfur carrier required for 2-thiolation of mcm(5)S(2)U at tRNA wobble positions of cytosolic tRNA(Lys), tRNA(Glu) and tRNA(Gln). Serves as sulfur donor in tRNA 2- thiolation reaction by being thiocarboxylated (-COSH) at its C- terminus by MOCS3.

The sulfur is then transferred to tRNA to form 2-thiolation of mcm(5)S(2)U. also functions as a ubiquitin-like protein (UBL) which is covalently conjugated through an isopeptide bond to lysine residues of target proteins like MOCS3, ATPBD3, CTU2, USP15 and CAS.