| Type: | Domain | Name: | Molybdopterin-guanine dinucleotide biosynthesis protein B (MobB) domain |
| Description: | The MobB domain is similar to that of the urease accessory protein UreG and the hydrogenase accessory protein HypB, both GTP hydrolases involved in loading nickel into the metallocentres of their respective target enzymes. It is involved in the final step of molybdenum-cofactor biosynthesis. While its precise function has not been identified it is thought to be involved in the transfer of a guanine dinucleotide moiety to molybdopterin, as it shows GTP-binding and weak GTPase activity []. The MobB protein () from Escherichia coli, which is comprised of this domain, is a homodimer []. Each molecule is composed of two distinct regions - an outer region comprised of 6 beta-strands and three alpha helices, and an inner region comprised of a two-strand beta hairpin followed by an alpha helix. These regions require interaction with the second monomer to allow proper folding to occur. The two monomers are intertwined and form an extensive 16-stranded beta-sheet. While the active site could not be positively identified, the presence of highly conserved residues suggests the substrate binding site occurs in the central solvent channel.The majority of molybdenum-containing enzymes utilise a molybdenum cofactor (MoCF or Moco) consisting of a Mo atom coordinated via a cis-dithiolene moiety to molybdopterin (MPT). MoCF is ubiquitous in nature, and the pathway for MoCF biosynthesis is conserved in all three domains of life. MoCF-containing enzymes function as oxidoreductases in carbon, nitrogen, and sulphur metabolism [, ]. In Escherichia coli, biosynthesis of MoCF is a three stage process. It begins with the MoaA and MoaC conversion of GTP to the meta-stable pterin intermediate precursor Z. The second stage involves MPT synthase (MoaD and MoaE), which converts precursor Z to MPT; MoeB is involved in the recycling of MPT synthase. The final step in MoCF synthesis is the attachment of mononuclear Mo to MPT, a process that requires MoeA and which is enhanced by MogA in an Mg2 ATP-dependent manner []. MoCF is the active co-factor in eukaryotic and some prokaryotic molybdo-enzymes, but the majority of bacterial enzymes requiring MoCF, need a modification of MTP for it to be active; MobA is involved in the attachment of a nucleotide monophosphate to MPT resulting in the MGD co-factor, the active co-factor for most prokaryotic molybdo-enzymes. Bacterial two-hybrid studies have revealed the close interactions between MoeA, MogA, and MobA in the synthesis of MoCF []. Moreover the close functional association of MoeA and MogA in the synthesis of MoCF is supported by fact that the known eukaryotic homologues to MoeA and MogA exist as fusion proteins: CNX1 () of Arabidopsis thaliana(Mouse-ear cress), mammalian Gephryin (e.g. ) and Drosophila melanogaster(Fruit fly) Cinnamon () []. | Short Name: | MobB_dom |
| DB identifier | Type | Name |
|---|---|---|
| IPR012182 | Family | Bifunctional molybdenum cofactor biosynthesis MobB/MoeA |
| DB identifier | Type | Name |
|---|---|---|
| IPR027417 | Domain | P-loop containing nucleoside triphosphate hydrolase |
| DB identifier | UniProt Accession | Secondary Identifier | Organism Name | Length |
|---|---|---|---|---|
| 31973.m000022 | B9TGN8 | PAC:16825263 | Ricinus communis |
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