molybdopterin synthase sulfur carrier subunit; MOCO1-A; molybdenum cofactor synthesis protein 2 small subunit; molybdenum cofactor synthesis protein 2A; MOCS2A; molybdopterin-synthase small subunit; sulfur carrier protein MOCS2A (MOCS2, MOCO1)

Function

• acts as a sulfur carrier required for molybdopterin biosynthesis
• component of the molybdopterin synthase complex that catalyzes 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
• cofactor biosynthesis; molybdopterin biosynthesis
• C-terminal thiocarboxylation occurs in 2 steps, it is first acyl-adenylated (-COAMP) via the hesA/moeB/thiF part of MOCS3, then thiocarboxylated (-COSH) via the rhodanese domain of MOCS3

Structure

belongs to the moaD family, MOCS2A subfamily

Compartment

cytoplasm, cytosol

Expression

• widely expressed
• highest expression in heart & skeletal muscle
• lesser expression in brain, kidney & pancreas
• very low expression in lung & peripheral blood leukocytes

Pathology

• defects in MOCS2 are the cause of molybdenum cofactor deficiency type B

Notes

• produced by a bicistronic gene which also produces the large subunit (MOCS2B) from an overlapping reading frame
• expression of these 2 proteins are related since a mutation that removes the start codon of the small subunit (MOCS2A) also impairs expression of the large subunit (MOCS2B)

More general terms

• molybdenum cofactor synthesis protein

Component of

• molybdopterin synthase complex

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=4338
• OMIM: https://mirror.omim.org/entry/252150
• OMIM: https://mirror.omim.org/entry/603708
• UniProt: http://www.uniprot.org/uniprot/O96033.html