Anti-GTP cyclohydrolase 1 antibodies are used in the immunodetection of the protein encoded by the GCH1 gene. In humans, the canonical protein has a reported length of 250 amino acid residues and a mass of 27.9 kDa. Its subcellular localization is in the nucleus and cytoplasm. Alternative splicing is reported to yield 4 different isoforms for this protein. A member of the GTP cyclohydrolase I protein family, it is known to be involved with the assembly of protein complexes. Post-translational modifications have been described, including phosphorylation. Other names for this target antigen include DYT5, DYT5a, GCH, GTP-CH-1, GTPCH1, HPABH4B, GTP cyclohydrolase I, and DYT14.