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HMDB Protein ID HMDBP02015
Secondary Accession Numbers
  • 7471
Name Molybdopterin synthase sulfur carrier subunit
  1. MOCO1-A
  2. MOCS2A
  3. Molybdenum cofactor synthesis protein 2 small subunit
  4. Molybdenum cofactor synthesis protein 2A
  5. Molybdopterin-synthase small subunit
  6. Sulfur carrier protein MOCS2A
Gene Name MOCS2
Protein Type Enzyme
Biological Properties
General Function Involved in Mo-molybdopterin cofactor biosynthetic process
Specific Function Acts as a sulfur carrier required for molybdopterin biosynthesis. Component of the molybdopterin synthase complex that catalyzes the conversion of precursor Z into molybdopterin by mediating the incorporation of 2 sulfur atoms into precursor Z to generate a dithiolene group. In the complex, serves as sulfur donor by being thiocarboxylated (-COSH) at its C-terminus by MOCS3. After interaction with MOCS2B, the sulfur is then transferred to precursor Z to form molybdopterin.
  • Folate biosynthesis
  • molybdopterin biosynthesis
  • Sulfur relay system
Cyclic pyranopterin monophosphate + Sulfur donor → Molybdopterin details
GO Classification
Biological Process
water-soluble vitamin metabolic process
Mo-molybdopterin cofactor biosynthetic process
Cellular Component
molybdopterin synthase complex
Molecular Function
nucleotide binding
metabolic process
coenzyme biosynthetic process
sulfur metabolic process
cellular metabolic process
cofactor metabolic process
coenzyme metabolic process
mo-molybdopterin cofactor biosynthetic process
Cellular Location
  1. Cytoplasm
  2. cytosol
Gene Properties
Chromosome Location 5
Locus 5q11
Gene Sequence
>267 bp
Protein Properties
Number of Residues 88
Molecular Weight 9755.235
Theoretical pI 4.702
Pfam Domain Function
Signals Not Available
Transmembrane Regions Not Available
Protein Sequence
>Molybdopterin synthase sulfur carrier subunit
GenBank ID Protein 4262372
UniProtKB/Swiss-Prot ID O96033
UniProtKB/Swiss-Prot Entry Name MOC2A_HUMAN
PDB IDs Not Available
GenBank Gene ID AF091871
GeneCard ID MOCS2
GenAtlas ID MOCS2
General References
  1. Stallmeyer B, Drugeon G, Reiss J, Haenni AL, Mendel RR: Human molybdopterin synthase gene: identification of a bicistronic transcript with overlapping reading frames. Am J Hum Genet. 1999 Mar;64(3):698-705. [PubMed:10053003 ]
  2. Sloan J, Kinghorn JR, Unkles SE: The two subunits of human molybdopterin synthase: evidence for a bicistronic messenger RNA with overlapping reading frames. Nucleic Acids Res. 1999 Feb 1;27(3):854-8. [PubMed:9889283 ]
  3. Leimkuhler S, Freuer A, Araujo JA, Rajagopalan KV, Mendel RR: Mechanistic studies of human molybdopterin synthase reaction and characterization of mutants identified in group B patients of molybdenum cofactor deficiency. J Biol Chem. 2003 Jul 11;278(28):26127-34. Epub 2003 May 5. [PubMed:12732628 ]
  4. Matthies A, Rajagopalan KV, Mendel RR, Leimkuhler S: Evidence for the physiological role of a rhodanese-like protein for the biosynthesis of the molybdenum cofactor in humans. Proc Natl Acad Sci U S A. 2004 Apr 20;101(16):5946-51. Epub 2004 Apr 8. [PubMed:15073332 ]
  5. Matthies A, Nimtz M, Leimkuhler S: Molybdenum cofactor biosynthesis in humans: identification of a persulfide group in the rhodanese-like domain of MOCS3 by mass spectrometry. Biochemistry. 2005 May 31;44(21):7912-20. [PubMed:15910006 ]
  6. Krepinsky K, Leimkuhler S: Site-directed mutagenesis of the active site loop of the rhodanese-like domain of the human molybdopterin synthase sulfurase MOCS3. Major differences in substrate specificity between eukaryotic and bacterial homologs. FEBS J. 2007 Jun;274(11):2778-87. Epub 2007 Apr 25. [PubMed:17459099 ]
  7. Schmitz J, Chowdhury MM, Hanzelmann P, Nimtz M, Lee EY, Schindelin H, Leimkuhler S: The sulfurtransferase activity of Uba4 presents a link between ubiquitin-like protein conjugation and activation of sulfur carrier proteins. Biochemistry. 2008 Jun 17;47(24):6479-89. doi: 10.1021/bi800477u. Epub 2008 May 21. [PubMed:18491921 ]
  8. Reiss J, Dorche C, Stallmeyer B, Mendel RR, Cohen N, Zabot MT: Human molybdopterin synthase gene: genomic structure and mutations in molybdenum cofactor deficiency type B. Am J Hum Genet. 1999 Mar;64(3):706-11. [PubMed:10053004 ]
  9. Johnson JL, Coyne KE, Rajagopalan KV, Van Hove JL, Mackay M, Pitt J, Boneh A: Molybdopterin synthase mutations in a mild case of molybdenum cofactor deficiency. Am J Med Genet. 2001 Nov 22;104(2):169-73. [PubMed:11746050 ]
  10. Leimkuhler S, Charcosset M, Latour P, Dorche C, Kleppe S, Scaglia F, Szymczak I, Schupp P, Hahnewald R, Reiss J: Ten novel mutations in the molybdenum cofactor genes MOCS1 and MOCS2 and in vitro characterization of a MOCS2 mutation that abolishes the binding ability of molybdopterin synthase. Hum Genet. 2005 Oct;117(6):565-70. Epub 2005 Jul 14. [PubMed:16021469 ]
  11. Hahnewald R, Leimkuhler S, Vilaseca A, Acquaviva-Bourdain C, Lenz U, Reiss J: A novel MOCS2 mutation reveals coordinated expression of the small and large subunit of molybdopterin synthase. Mol Genet Metab. 2006 Nov;89(3):210-3. Epub 2006 Jun 5. [PubMed:16737835 ]