MOSC1 (MOCO sulphurase C-terminal domain containing 1), also known as MARC1, is a 337 amino acid mitochondrial protein that is thought to function as an oxidoreductase. Existing as three alternatively spliced isoforms, MOSC1 contains one MOSC domain and binds molybdenum as a cofactor. The gene encoding MOSC1 maps to human chromosome 1, which spans 260 million base pairs, contains over 3,000 genes and comprises nearly 8 % of the human genome. Chromosome 1 houses a large number of disease-associated genes, including those that are involved in familial adenomatous polyposis, Stickler syndrome, Parkinson's disease, Gaucher disease, schizophrenia and Usher syndrome. Aberrations in chromosome 1 are found in a variety of cancers, including head and neck cancer, malignant melanoma and multiple myeloma.