Plays a central role in 2-thiolation of mcm(5)S(2)U at tRNA wobble positions of tRNA(Lys), tRNA(Glu) and tRNA(Gln). May act by forming a heterodimer with CTU1/ATPBD3 that ligates sulfur from thiocarboxylated URM1 onto the uridine of tRNAs at wobble position. tRNA modification; 5-methoxycarbonylmethyl-2-thiouridine-tRNA biosynthesis. Component of a complex at least composed of URM1, CTU2/NCS2 and CTU1/ATPBD3. The disease may be caused by variants affecting the gene represented in this entry. A homozygous synonymous variant at codon 247 has been identified in 3 consanguineous families. This variant impairs normal splicing, causing a frameshift resulting in a premature termination codon. Incomplete sequence. Belongs to the CTU2/NCS2 family.