The Biosynthesis of the Molybdenum Cofactor inEscherichia coliand Its Connection to FeS Cluster Assembly and the Thiolation of tRNA

Abstract

The thiolation of biomolecules is a complex process that involves the activation of sulfur. The L-cysteine desulfurase IscS is the main sulfur mobilizing protein in Escherichia coli that provides the sulfur from L-cysteine to several important biomolecules in the cell such as iron sulfur (FeS) clusters, molybdopterin (MPT), thiamine, and thionucleosides of tRNA. Various proteins mediate the transfer of sulfur from IscS to various biomolecules using different interaction partners. A direct connection between the sulfur-containing molecules FeS clusters, thiolated tRNA, and the molybdenum cofactor (Moco) has been identified. The first step of Moco biosynthesis involves the conversion of 5′GTP to cyclic pyranopterin monophosphate (cPMP), a reaction catalyzed by a FeS cluster containing protein. Formed cPMP is further converted to MPT by insertion of two sulfur atoms. The sulfur for this reaction is provided by the L-cysteine desulfurase IscS in addition to the involvement of the TusA protein. TusA is also involved in the sulfur transfer for the thiolation of tRNA. This review will describe the biosynthesis of Moco in E. coli in detail and dissects the sulfur transfer pathways for Moco and tRNA and their connection to FeS cluster biosynthesis.

Diverse Mechanisms of Sulfur Decoration in Bacterial tRNA and Their Cellular Functions

“…In Gram-negative E. coli , which uses the housekeeping IscS for sulfur mobilization to all thiocofactors [11,53,54], the Tus proteins also participate in additional metabolic pathways [71,175,176,177]. The multi-functionality of these and other enzymes in thiocofactor pathways has been attributed to the utilization of one major cysteine desulfurase (i.e., IscS) for all thiocofactors in Gram-negative bacteria and simultaneously demonstrates the resulting complexity of sulfur trafficking in these organisms [178,179]. The recruitment of small sulfur acceptor proteins or sulfurtransferase domains within individual pathways can be seen as a mechanistic strategy for controlling sulfur flux in organisms such as E. coli that utilize a master sulfur donor.…”

“…Recent studies have revealed that thio-modifications participate in other cellular processes, including metabolism, stress response, and regulatory functions [24]. Several recent models have proposed interconnectivity between biosynthesis of thionucleosides and other thiocofactors in bacteria, providing another potential regulatory mechanism for thiocofactor biosynthesis [178,179]. In E. coli , s 2 C and ms 2 i 6 A biosynthetic pathways utilize [Fe-S] cluster dependent proteins, as do the pathways for ms 2 i 6 A and ms 2 t 6 A biosyntheses in B. subtilis .…”

An overview of the biological metal uptake pathways in Pseudomonas aeruginosa

“…Molybdenum (Mo) is stable in aqueous solutions as the molybdate ion MoO 22 4 and this form is thus the only relevant source of Mo for biological systems (Williams and Fra usto da Silva, 2002). Mo is redox-active under physiological conditions, alternating between the oxidation states 61 and 41; it is a common cofactor in various oxidoreductase enzymes, which are involved in key transformations in the metabolism of nitrogen, sulfur, and carbon compounds (nitrogenase, sulfite oxidase, nitrate reductase, and many others) (Leimk€ uhler, 2014). Mo plays an essential role in anaerobic respiration in P. aeruginosa, in the first step of the nitrate reduction Pseudomonas and metals 3239 pathway (Philippot and Højberg, 1999;Arai, 2011;Iobbi-Nivol and Leimk€ uhler, 2013).…”

Optimization of overexpression of a chaperone protein of steroid C25 dehydrogenase for biochemical and biophysical characterization

“…In bis -MGD, the molybdenum atom is coordinated through two dithiolene groups of two MGD moieties [17–19]. In E. coli , the in vivo process of production of bis -MGD cofactor consists of four main steps: a) the conversion of GTP into cyclic pyranopterin monophosphate (cPMP) by S-adenosyl methionine (SAM)-dependent radical enzymes [20] and cyclic pyranopterin monophosphate synthase accessory protein, b) the insertion of sulfur and formation of molybdopterin (MPT) by MPT synthase [21,22], c) the insertion of molybdenum, which is sequestered as a molybdate oxyanion (MoO 4 2− ) [23] into MPT by molybdopterin adenylyltransferase (MogA) [24] and molybdopterin molybdenumtransferase (MoeA) [18] and d) the further modification of Moco to form a dinucleotide derivative of Moco, the MPT-guanine dinucleotide (MGD) cofactor.…”