EC Number   |
General Information |
Reference |
|---|
   1.4.9.1 | evolution |
the qhp genes are very widely distributed, not only in many Gram-negative species but also in a few Gram-positive bacteria, bacterial distribution of qhp and associated genes, overview. The subunits constituting QHNDH are encoded by ORF1 (alpha subunit), ORF4 (beta subunit), and ORF3 (gamma subunit). Of the other genes in the operon, ORF2 encodes an [Fe-S] cluster and S-adenosylmethionine (SAM)-binding protein, a member of the radical SAM superfamily, and ORF5 encodes a protein of approximately 22.5 kDa belonging to subfamily S8A of peptidase family S8 (the subtilisin family) with the conserved Asp/His/Ser catalytic triad characteristic of this subfamily |
741905 |
| 1.4.9.1 | malfunction |
the genes mauF and mauE are membrane proteins with no homology to characterized proteins, and are thought to be involved in transport of MADH subunits into the periplasm. Knocking out either gene leads to no detectable beta-subunit in the periplasm, and an unusual beta-subunit leader sequence is consistent with it being trafficked by a specific transporter. The loss of mauF and mauE additionally leads to a drastic reduction in alpha-subunit. The third gene, mauD, is homologous to disulfide isomerases, and is likely specific to the MADH beta-subunit, which has six disulfides. In the absence of mauD, periplasmic alpha-subunit levels are close to normal, but again there is no detectable beta-subunit implying that the disulfides are key to beta-subunit stability. When the final required gene, mauG, is knocked out, there are normal levels of MADH alpha- and beta-subunit in the periplasm, but no methylamine dehydrogenase activity is present. This has focused attention on the mauG gene product as a likely participant in TTQ biosynthesis |
742338 |
| 1.4.9.1 | more |
MauG is a diheme enzyme responsible for the posttranslational modification of two tryptophan residues in pre-MADH to form the tryptophan tryptophylquinone, TTQ, cofactor of methylamine dehydrogenase. MauG catalyzes a six electron oxidation to complete TTQ biosynthesis. Oxidizing equivalents may be provided by three mol of either O2, plus an electron donor, or H2O2 |
713510 |
| 1.4.9.1 | more |
QM/MM molecular dynamics simulations at room temperature generate a multidimensional thermal free-energy landscape without restriction of the degrees of freedom beyond a multidimensional reaction subspace mapping two rather similar pathways for the underlying proton transfer to one of two aspartate carboxyl oxygen atoms, termed OD1 and OD2, which hydrogen bond with Thr122 and Trp108, respectively. Despite significant large-amplitude motion perpendicular to the one-dimensional proton transfer coordinate, due to fluctuations of the donor-acceptor distance of about 3 a, it is found that the one-dimensional proton transfer free-energy profiles are essentially identical to the minimum free-energy pathways on the multidimensional free-energy landscapes for both proton transfer channels. Proton transfer to one of the acceptor oxygen atoms (the OD2 site) is slightly favored in methylamine dehydrogenase both kinetically and thermodynamically. Modeling is based on the crysta structure of the substrate-free enzyme MADH from Paracoccus denitrificans resolved at 1.75 A, PDB ID 2BBK |
742302 |
| 1.4.9.1 | more |
steady-state MauG-depedent TTQ biosynthesis using quinol MADH as a substrate and single-turnover kinetics of the reaction of bis-Fe(IV) MauG with quinol MADH, overview |
711254 |
| 1.4.9.1 | more |
structural features of the gamma subunit clearly indicate that it must undergo multiple posttranslational modifications before it can form an active QHNDH complex with the alpha and beta subunits. The qhpG gene encodes a putative FAD-dependent monooxygenase, which is required for the generation of the quinone cofactor in the gamma subunit. The qhpR gene encodes an AraC family transcriptional regulator, which activates expression of the qhp operon in response to the addition of n-butylamine to the culture medium. The structural genes encoding the three QHNDH subunits constitute an operon harboring six apparent open reading frames (ORFs) that are transcribed in a coordinated manner upon addition of amines to the culture medium. QhpF serves as an efflux ABC transporter for translocation of the gamma subunit of QHNDH into the periplasm |
741905 |
| 1.4.9.1 | physiological function |
MADH catalyzes the oxidative deamination of methylamine to formaldehyde and ammonia, a reaction which allows the host bacterium to use methylamine as a sole source of carbon, nitrogen and energy. MADH donates the electrons which it extracts from methylamine to the mauC gene product, a type 1 copper protein named amicyanin, which in turn transfers electrons to cytochrome c-551i. The catalytic cofactor of MADH is tryptophan tryptophyquinone, TTQ |
741759 |
| 1.4.9.1 | physiological function |
the diheme enzyme MauG catalyzes a six electron oxidation that is required for the posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived cofactor, tryptophan tryptophylquinone (TTQ). The substrate for MauG that undergoes this posttranslational modification is a precursor protein of MADH (preMADH). It possesses a monohydroxylated residue betaTrp57. The reactions catalyzed by MauG occur in the following order: covalent cross-linking of monohydroxylated betaTrp57 to betaTrp108, incorporation of a second oxygen atom into the side chain of betaTrp57, and oxidation of the quinol species to the quinone. Catalysis requires long-range electron transfer because preMADH does not make direct contact with either heme of MauG. The electron transfer occurs via a hole-hopping mechanism in which Trp residues of MauG are reversibly oxidized |
741893 |
| 1.4.9.1 | physiological function |
the diheme enzyme MauG catalyzes oxidative post-translational modifications of a protein substrate, precursor protein of methylamine dehydrogenase (preMADH), that binds to the surface of MauG. Tinding of preMADH to MauG affects both the coordination state of the ferric high-spin heme, and the kinetic mechanism of the autoreduction of the bis-FeIV hemes. Binding sructure analysis, overview |
742527 |
