Anti-MSR antibodies enable researchers to detect and measure the MSR antigen in biological samples. This target is a reported synonym of the MTRR gene, which encodes 5-methyltetrahydrofolate-homocysteine methyltransferase reductase. This protein is known to function in metabolic processes, among other biological roles. The human version of MSR has a canonical amino acid length of 698 residues and a protein mass of 77.7 kilodaltons, although 2 isoforms have been identified. It is reported to be localized in the cytoplasm of cells and widely expressed in many tissue types.