CTU2 is a 515 amino acid cytoplasmic protein that plays a role in the 2-thiolation of mcm(5)S(2)U at wobble positions of tRNA. CTU2 forms a complex with CTU1 and Urm1, and may also form a separate heterodimer with CTU1 to ligate sulfur from thiocarboxylated Urm1 onto tRNA. Existing as three alternatively spliced isoforms, the gene encoding CTU2 maps to human chromosome 16q24.3. Chromosome 16 encodes over 900 genes and comprises nearly 3% of the human genome. The GAN gene is located on chromosome 16 and, with mutation, may lead to giant axonal neuropathy, a nervous system disorder characterized by increasing malfunction with growth. The rare disorder Rubinstein-Taybi syndrome is also associated with chromosome 16, as is Crohn's disease, which is a gastrointestinal inflammatory condition.