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

Figure 4

Synthesis of cPMP from 5′GTP. All carbon atoms of the 5′GTP are found within cPMP. The C8 atom from the guanine ring is inserted between the C2′ and C3′ atoms of the ribose. This reaction is catalyzed by the MoaA protein, an S-adenosylmethionine- (SAM-) dependent enzyme. MoaA forms a dimer with two [4Fe4S] clusters bound to each monomer. The trimeric MoaC protein is suggested to cleave the pyrophosphate group of the cyclic intermediate. cPMP is shown in the tetrahydropyrano form with a keto group at the C1′ position, as suggested from the crystal structure [55].