Disease relevance of methanamine

• The ammonium/methylammonium transport (Amt) proteins of enteric bacteria and their homologues, the methylammonium/ammonium permeases of Saccharomyces cerevisiae, are required for fast growth at very low concentrations of the uncharged species NH(3) [1].
• Under nitrogen starvation conditions, Corynebacterium glutamicum was found to take up methylammonium at a rate of 20 +/- 5 nmol.min-1.(mg dry weight)-1 [2].
• Ammonium/methylammonium permeases of a Cyanobacterium. Identification and analysis of three nitrogen-regulated amt genes in synechocystis sp. PCC 6803 [3].
• Ammonium transporters whose activity can be probed with [14C]methylammonium have been described in several organisms including some cyanobacteria, and amt genes encoding ammonium/methylammonium permeases have been recently identified in yeast, Arabidopsis thaliana, and some bacteria [3].
• Evidence for a methylammonium-binding site on methylamine dehydrogenase of Thiobacillus versutus [4].

High impact information on methanamine

• The substrates ammonium and methylammonium have been used for cocrystallization experiments with Amt-1, but the identification of binding sites that are distinct from water positions is not unambiguous [5].
• Together with our previous studies, current results are in accord with the view that Amt and methylammonium/ammonium permease proteins increase the rate of diffusion of the uncharged species NH(3) across the cytoplasmic membrane [1].
• Based on the organismal, organ, and tissue distribution of Rh proteins, and on our evidence that their only known paralogues, the ammonium and methylammonium transport proteins (also called methylammonium permeases), are gas channels for NH(3), we recently speculated that Rh proteins are biological gas channels for CO(2) [6].
• In bacteria, however, ATP-dependent conversion of methylammonium to gamma-N-methylglutamine by glutamine synthetase precludes its use in assessing concentrative transport across the cytoplasmic membrane [7].
• Thus, in fungi as in bacteria, subsequent energy-dependent utilization of methylammonium precludes its use in assessing active transport across the cytoplasmic membrane [7].

Chemical compound and disease context of methanamine

• Hypertrophy was also induced by methylammonium chloride, a related weak base, but not by tetramethylammonium chloride, a weak base analogue that can neither accept nor donate protons [8].

Biological context of methanamine

• The methylammonium uptake showed Michaelis-Menten kinetics with an Km of 44 +/- 7 microM and was completely inhibited by the addition of 10 microM ammonium [2].
• From the pH optimum and the accumulation of methylammonium in equilibrium, it could be deduced that only one net charge is transported and, thus, that methylammonium is taken up in its protonated form via an uniport mechanism [2].
• Methylammonium uptake was strictly dependent on the membrane potential [2].
• Open reading frame sll0108 (amt1) was responsible for a high affinity uptake activity (Ks for methylammonium, 2.7 microM), whereas open reading frames sll1017 (amt2) and sll0537 (amt3) made minor contributions to uptake at low substrate concentrations [3].
• Characterisation of the glnK-amtB operon and the involvement of AmtB in methylammonium uptake in Azorhizobium caulinodans [9].

Anatomical context of methanamine

• AtTIP2;1- and AtTIP2;3-mediated methylammonium detoxification in yeast depended on a functional vacuole, which was in agreement with the subcellular localization of green fluorescent protein-fusion proteins on the tonoplast in planta [10].
• In accordance with its localization, human RhBG mediates saturable, electroneutral transport of the ammonium analogue methylammonium when heterologously expressed in Xenopus oocytes [11].
• In rat yolk sacs incubated in vitro, the rates of degradation of endogenous [3H]leucine-labelled proteins and of pinocytically ingested 125I-labelled bovine serum albumin were both decreased in the presence of either ammonium, methylammonium or ethylammonium ions (0-20 mM) or much lower concentrations of chloroquine (0-500 microM) [12].
• Thus, this work provides directly the missing evidence for the hypothesized role played by the wider vestibule site of AmtB at the periplasmic side of the membrane in "recruiting" NH(4)(+) or methylammonium ions as proposed by Khademi et al [13].
• Glutamine synthetase activity of cells cultured with ammonium was 33% that of N2-fixing cultures, but activity was unaffected by incubation with methylammonium [14].

Associations of methanamine with other chemical compounds

• Accordingly, ptk2 mutants exhibited reduced uptake of lithium and methylammonium [15].
• (The term ammonium is used to denote both NH3 and NH4+ and chemical symbols are used when specificity is required.) We therefore developed a yeast (Saccharomyces cerevisiae) complementation approach and isolated two Arabidopsis (Arabidopsis thaliana) genes that conferred tolerance to the toxic ammonium analog methylammonium in yeast [10].
• The organic cations, hydrazinium, methylammonium, ethanolammonium and Tris, were measureably permeant, and permeability ratios varied inversely with the molecular size of the cation [16].
• Some small amines permeate Ih channels, with the following permeability ratios (PX/PK):NH4+, 0.17; methylammonium, 0.06; and hydrazine, 0.04 [17].
• It was found that, not only methylammonium+, but also dimethylammonium+ and ethylammonium+ were permeant with permeability ratios of 0.6, 0.14 and 0.16 respectively [18].

Gene context of methanamine

• Instead, we find that Hor7p-overproducing cells display an increased resistance to high salt, sensitivity to low pH, and a reduced uptake of methylammonium, an indicator of the plasma membrane potential [19].
• RhCG mediated the electroneutral transport of methylammonium (MeA), which saturated with Km = 3.8 mM at pHo 7 [20].
• In contrast to transporters of the AMT1 family, however, AtAMT2 did not transport the ammonium analogue, methylammonium [21].
• glnA mutations conferring resistance to methylammonium in Escherichia coli K12 [22].
• Methylammonium recognition involves two aromatic residues, not the three-residue aromatic cage used by chromodomains of HP1 and Polycomb proteins [23].

Analytical, diagnostic and therapeutic context of methanamine

• One mutant in the largest class had an insert in the AMT4 gene, and the insert cosegregated with methylammonium resistance in genetic crosses [24].
• Sequence analysis revealed that one P(II) protein-encoding gene, glnB, was adjacent to a glnA gene (encoding glutamine synthetase) and that two other P(II) protein-encoding genes, identified as glnK1 and glnK2, were located upstream of amtB1 and amtB2, respectively, genes which in other organisms encode ammonium (or methylammonium) transporters [25].
• The analysis of intracellular metabolites using thin-layer chromatography and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry indicated that methylammonium was rapidly metabolized to N-methylglutamate via gamma-N-methylglutamine [26].
• Discrimination of methylammonium from organic ammonium ions using ion-selective electrodes based on calix[4]arene-crown-6 conjugates [27].

References