The Biosynthesis of the Molybdenum Cofactor in Escherichia coli and Its Connection to FeS Cluster Assembly and the Thiolation of tRNA

Figure 2

The biosynthesis of Moco in E. coli. Shown is a scheme of the biosynthetic pathway for Moco biosynthesis in E. coli and the proteins involved in this pathway. Mo-MPT is formed from 5′GTP with cPMP, MPT, and MPT-AMP as intermediates. Mo-MPT is directly inserted into enzymes of the sulfite oxidase family. For enzymes of the DMSO reductase family, Moco is further modified by formation of a bis-Mo-MPT intermediate and further addition of a GMP molecule to each MPT unit, forming the bis-MGD cofactor. Both reactions are catalyzed by the MobA protein. For enzymes of the xanthine oxidase family in E. coli, Mo-MPT is further modified by the addition of CMP to form the MCD form of the cofactor. Additionally, a terminal sulfur ligand is added to the molybdenum site, generating sulfurated MCD. An additional ligand at the Mo-center usually is a hydroxo-group. The names of the proteins involved in the reactions are colored in red, and additional molecules required for the reactions are shown in blue.