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Editing of the gut microbiota reduces carcinogenesis in mouse models of colitis-associated colorectal cancer

Chronic inflammation and gut microbiota dysbiosis, in particular the bloom of genotoxin-producing E. coli strains, are risk factors for the development of colorectal cancer. Here, we sought to determine whether precision editing of gut microbiota metabolism and composition could decrease the risk for tumor development in mouse models of colitis-associated colorectal cancer (CAC). Expansion of experimentally introduced E. coli strains in the azoxymethane/dextran sulfate sodium colitis model was driven by molybdoenzyme-dependent metabolic pathways. Oral administration of sodium tungstate inhibited E. coli molybdoenzymes and selectively decreased gut colonization with genotoxin-producing E. coli and other Enterobacteriaceae. Restricting the bloom of Enterobacteriaceae decreased intestinal inflammation and reduced the incidence of colonic tumors in two models of CAC, the azoxymethane/dextran sulfate sodium colitis model and azoxymethane-treated, Il10-deficient mice. We conclude that metabolic targeting of protumoral Enterobacteriaceae during chronic inflammation is a suitable strategy to prevent the development of malignancies arising from gut microbiota dysbiosis.

W. H. Zhu, N. Miyata, M. G. Winter, A. Arenales, E. R. Hughes, L. Spiga, J. Kim, L. Sifuentes-Dominguez, P. Starokadomskyy, P. Gopal, M. X. Byndloss, R. L. Santos, E. Burstein, and S. E. Winter,Editing of the gut microbiota reduces carcinogenesis in mouse models of colitis-associated colorectal cancer, Journal of Experimental Medicine, 2019, 216, 2378-2393.


Copper iron, manganese, zinc

Spleen iron, moybdenum, and manganese concentrations are coregulated in hepcidin-deficient and secondary iron overload models in mice

Iron excess increases the hepatic expression of hepcidin, the systemic iron metabolism regulator that favors iron sequestration in the spleen. Genetic iron overload related to hepcidin insufficiency decreases the spleen iron concentration and increases hepatic iron concentration, whereas during secondary iron overload, the hepcidin expression increases together with spleen iron concentration in addition to hepatic iron concentrations increase. Links between iron metabolism and other metals being suggested, our aim was to investigate, during iron overload, the relationships between the hepatic hepcidin expression level and the hepatic and splenic concentrations of iron, manganese, copper, zinc, and moybdenum, determined using inductively coupled plasma mass spectrometry. Hepcidin-deficient mice, secondary iron overload mice models, and their respective controls were studied. Spleen moybdenum and manganese concentrations paralleled the modulation of both spleen iron concentrations, increasing in secondary iron overload and decreasing in hepcidin deficiency related iron overload, as well as hepatic hepcidin mRNA expression. Our data suggest that iron, manganese, and moybdenum metabolisms could share mechanisms controlling their distribution that are associated to hepcidin modulation. In diseases with abnormal hepcidin levels, including chronic inflammation, special attention should be paid to those metals that can participate with the phenotype.-Cavey, T., Latour, C., Island, M.-L., Leroyer, P., Guggenbuhl, P., Coppin, H., Roth, M.-P., Bendavid, C., Brissot, P., Ropert, M., Loreal, O. Spleen iron, moybdenum, and manganese concentrations are coregulated in hepcidin-deficient and secondary iron overload models in mice.

T. Cavey, C. Latour, M. L. Island, P. Leroyer, P. Guggenbuhl, H. Coppin, M. P. Roth, C. Bendavid, P. Brissot, M. Ropert, and O. Loreal,Spleen iron, moybdenum, and manganese concentrations are coregulated in hepcidin-deficient and secondary iron overload models in mice, Faseb Journal, 2019, 33, 11072-11081.


Determination of Ligand Profiles for Pseudomonas aeruginosa Solute Binding Proteins

Solute binding proteins (SBPs) form a heterogeneous protein family that is found in all kingdoms of life. In bacteria, the ligand-loaded forms bind to transmembrane transporters providing the substrate. We present here the SBP repertoire of Pseudomonas aeruginosa PAO1 that is composed of 98 proteins. Bioinformatic predictions indicate that many of these proteins have a redundant ligand profile such as 27 SBPs for proteinogenic amino acids, 13 proteins for spermidine/putrescine, or 9 proteins for quaternary amines. To assess the precision of these bioinformatic predictions, we have purified 17 SBPs that were subsequently submitted to high-throughput ligand screening approaches followed by isothermal titration calorimetry studies, resulting in the identification of ligands for 15 of them. Experimentation revealed that PA0222 was specific for gamma-aminobutyrate (GABA), DppA2 for tripeptides, DppA3 for dipeptides, CysP for thiosulphate, OpuCC for betaine, and AotJ for arginine. Furthermore, RbsB bound D-ribose and D-allose, ModA bound molybdate, tungstate, and chromate, whereas AatJ recognized aspartate and glutamate. The majority of experimentally identified ligands were found to be chemoattractants. Data show that the ligand class recognized by SPBs can be predicted with confidence using bioinformatic methods, but experimental work is necessary to identify the precise ligand profile.

M. Fernandez, M. Rico-Jimenez, A. Ortega, A. Daddaoua, A. I. Garcia Garcia, D. Martin-Mora, N. M. Torres, A. Tajuelo, M. A. Matilla, and T. Krell,Determination of Ligand Profiles for Pseudomonas aeruginosa Solute Binding Proteins, International journal of molecular sciences, 2019, 20, 5156


Amino acid and protein metabolism

Biological Interaction of Molybdenocene Dichloride with Bovine Serum Albumin Using Fluorescence Spectroscopy

Bioinorganic topics are ubiquitous in the inorganic chemistry curriculum; however, experiments to enhance understanding of related topics are scarce. In this proposed laboratory, upper undergraduate students assess the biological interaction of molybdenocene dichloride (Cp2MoCl2) with bovine serum albumin (BSA) by fluorescence spectroscopy. Specifically, learners study the quenching mechanism by performing a binding titration of-a bovine serum albumin (BSA) solution with molybdenocene dichloride at physiological pH at three temperatures to determine the biomolecular quenching constant as defined in the Stern-Volmer equation. The temperature dependency of the quenching constant allows estimation of thermodynamic parameters which in turn permits an assessment of the nature of the intermolecular interactions involved. This educational activity promotes graph interpretation and integration of concepts such as metallocene-protein interaction, fluorescence quenching, Gibbs energy, entropy, and enthalpy, where students learn to propose a quenching mechanism and to assess the intermolecular forces that may be involved. The proposed experiment can be implemented in various educational settings such as inorganic chemistry, biochemistry, biophysical chemistry, and analytical-chemistry.

M. Dominguez, J. E. Cortes-Figueroa, and E. Melendez,Biological Interaction of Molybdenocene Dichloride with Bovine Serum Albumin Using Fluorescence Spectroscopy, Journal of Chemical Education, 2018, 95, 152-157.

Amino acid and protein metabolism

Selective cleavage of pepsin by molybdenum metallopeptidase

In this study, the cleavage of protein by molybdenum cluster is reported for the first time. The protein target used is porcine pepsin.

The data presented in this study show that pepsin is cleaved to at least three fragments with molecular weights of ca 23, ca 19 and ca 16 kDa when the mixture of the protein and ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24.4H2O) was incubated at 37 degrees C for 24 h. No self cleavage of pepsin occurs at 37 degrees C, 24 h indicating that the reaction is mediated by the metal ions.

N-terminal sequencing of the peptide fragments indicated three cleavage sites of pepsin between Leu 112-Tyr 113, Leu 166-Leu 167 and Leu 178-Asn 179.

The cleavage reaction occurs after incubation of the mixture of pepsin and (NH4)6Mo7O24.4H2O for only 2 h. However, the specificity of the cleavage decreases when incubation time is longer than 48 h.

The mechanism for cleavage of pepsin is expected to be hydrolytic chemistry of the amide bonds in the protein backbone. (C) 2012 Elsevier Inc. All rights reserved

Yenjai, S., Malaikaew, P., Liwporncharoenvong, T., and Buranaprapuk, A., Selective cleavage of pepsin by molybdenum metallopeptidase, Biochemical and Biophysical Research Communications, 2012, 419, 126-129.

At low concentrations molybdenum has a beneficial effect on animal growth and protein synthesis in some species. Chicks grew more rapidly and had a higher haemoglobin count when 1-5 ppm Mo was added to the diet [Humphries, 1970; Norris, 1969; Probst, 1971]. The improvement in growth did not occur with diets containing 100 ppm Mo indicating some toxicity at this higher level. Molybdenum promotes protein synthesis in the red trout [Jurca and Matei, 1967]. Trout raised on a diet which included 0.126 g ammonium molybdate/100 kg forage were larger and better developed than those raised on fresh food and the protein content of the blood serum was increased. However, according to other work molybdenum may have an inhibitory effect on protein synthesis. Molybdenum (400 ppm) added to the diet of experimental rats did not affect digestion and absorption of nitrogen compounds but caused an increase in urinary excretion first as urea and ammonia and then as alpha-amino nitrogen [Johnson and Miller, 1963; Val chuk and Kovalskaya, 1970]. Urinary levels of alpha-amino nitrogen increased with increased dietary molybdenum and with increased time of feeding, and urea and ammonia decreased. Molybdenum inhibited incorporation of leucine into protein in a homogenised rat liver preparation (16% inhibition at 10-4 M Mo and 80% inhibition at 10-3 M) [Peive, 1968].

Humphries, W., Poultry and Egg Production, 1970, 12, 5, 8.
ILO, Occupational Exposure Limits, 2nd (revised) Edition, Occupational Safety and Health Series, 37, ILO Geneva 1980.
Norris, L. C., Feedstuffs, 1969, 9, 9.
Probst, K., Z. Tierphysiol. Tierernaehr. Futtermittelk., 1971, 27, 99.
Jurca, V. and Matei, D., An. Stiint. Univ. Al. 1. Cuza lasi Sect. IC 1967, 13, 115
Jurca, V., An. Stiint. Univ. Al. l. Cuza lasi Sect. IC, 1967, 13, 213.
Johnson, H. L. and Miller, R. F., J. Nutr., 1963, 81, 271.
Val chuk, N. K.and Kovalskaya, N. M., Gig. Sanit., 1970, 35, 99.
Peive, Ya. V. ,(ed.), Biol. Rol Molibdena, Sb. Tr. Simp. 1968 (Publ. 1972), Nauka, Moscow, U.S.S.R., 207, 235.

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