MOCS3

Function

Plays a central role in 2-thiolation of mcm(5)S(2)U at tRNA wobble positions of cytosolic tRNA(Lys), tRNA(Glu) and tRNA(Gln). Also essential during biosynthesis of the molybdenum cofactor. Acts by mediating the C-terminal thiocarboxylation of sulfur carriers URM1 and MOCS2A. Its N-terminus first activates URM1 and MOCS2A as acyl-adenylates (-COAMP), then the persulfide sulfur on the catalytic cysteine is transferred to URM1 and MOCS2A to form thiocarboxylation (-COSH) of their C-terminus. The reaction probably involves hydrogen sulfide that is generated from the persulfide intermediate and that acts as a nucleophile towards URM1 and MOCS2A. Subsequently, a transient disulfide bond is formed. Does not use thiosulfate as sulfur donor; NFS1 acting as a sulfur donor for thiocarboxylation reactions.

Pathway

tRNA modification; 5-methoxycarbonylmethyl-2-thiouridine-tRNA biosynthesis.

Cofactor biosynthesis; molybdopterin biosynthesis.

Sequence Similarities

In the N-terminal section; belongs to the HesA/MoeB/ThiF family. UBA4 subfamily.

Cellular localization

• Cytoplasm

Alternative names

UBA4, MOCS3, Adenylyltransferase and sulfurtransferase MOCS3, Molybdenum cofactor synthesis protein 3, Molybdopterin synthase sulfurylase, MPT synthase sulfurylase

Database links

swissprot:O95396 genbank:BC015939 entrezGene:27304 omim:609277