FunctionActs as a sulfur carrier required for 2-thiolation of mcm(5)S(2)U at tRNA wobble positions of tRNA(Lys), tRNA(Glu) and tRNA(Gln). Serves as sulfur donor in tRNA 2-thiolation reaction by 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. May also act as an ubiquitin-like protein that is covalently conjugated to other proteins; the relevance of such function is however unclear in vivo.
Post-translational modificationsC-terminal thiocarboxylation occurs in 2 steps, it is first acyl-adenylated (-COAMP) via the hesA/moeB/thiF part of MOCS3, then thiocarboxylated (-COSH) via the rhodanese domain of MOCS3.