title: Mode of action uncovered for the specific reduction of methane emissions from ruminants by the small molecule 3-nitrooxypropanol.
abstract: Ruminants, such as cows, sheep, and goats, predominantly ferment in their rumen plant material to acetate, propionate, butyrate, CO2, and methane. Whereas the short fatty acids are absorbed and metabolized by the animals, the greenhouse gas methane escapes via eructation and breathing of the animals into the atmosphere. Along with the methane, up to 12% of the gross energy content of the feedstock is lost. Therefore, our recent report has raised interest in 3-nitrooxypropanol (3-NOP), which when added to the feed of ruminants in milligram amounts persistently reduces enteric methane emissions from livestock without apparent negative side effects [Hristov AN, et al. (2015) Proc Natl Acad Sci USA 112(34):10663-10668]. We now show with the aid of in silico, in vitro, and in vivo experiments that 3-NOP specifically targets methyl-coenzyme M reductase (MCR). The nickel enzyme, which is only active when its Ni ion is in the +1 oxidation state, catalyzes the methane-forming step in the rumen fermentation. Molecular docking suggested that 3-NOP preferably binds into the active site of MCR in a pose that places its reducible nitrate group in electron transfer distance to Ni(I). With purified MCR, we found that 3-NOP indeed inactivates MCR at micromolar concentrations by oxidation of its active site Ni(I). Concomitantly, the nitrate ester is reduced to nitrite, which also inactivates MCR at micromolar concentrations by oxidation of Ni(I). Using pure cultures, 3-NOP is demonstrated to inhibit growth of methanogenic archaea at concentrations that do not affect the growth of nonmethanogenic bacteria in the rumen.
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849;
authors.forename: Evert C
authors.initials: EC
authors.lastname: Duin
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany;
authors.forename: Tristan
authors.initials: T
authors.lastname: Wagner
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany;
authors.forename: Seigo
authors.initials: S
authors.lastname: Shima
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849;
authors.forename: Divya
authors.initials: D
authors.lastname: Prakash
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849;
authors.forename: Bryan
authors.initials: B
authors.lastname: Cronin
authors.affiliation: Estación Experimental del Zaidín, Consejo Superior de Investigaciones Cientificas, 18008 Granada, Spain;
authors.forename: David R
authors.initials: DR
authors.lastname: Yáñez-Ruiz
authors.affiliation: Research Centre for Animal Nutrition and Health, DSM Nutritional Products France, 68305 Saint Louis, France;
authors.forename: Stephane
authors.initials: S
authors.lastname: Duval
authors.affiliation: Research and Development, DSM Nutritional Products, 4002 Basel, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Rümbeli
authors.affiliation: Research and Development, DSM Nutritional Products, 4002 Basel, Switzerland.
authors.forename: René T
authors.initials: RT
authors.lastname: Stemmler
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany; thauer@mpi-marburg.mpg.de maik.kindermann@dsm.com.
authors.forename: Rudolf Kurt
authors.initials: RK
authors.lastname: Thauer
authors.affiliation: Research and Development, DSM Nutritional Products, 4002 Basel, Switzerland thauer@mpi-marburg.mpg.de maik.kindermann@dsm.com.
authors.forename: Maik
authors.initials: M
authors.lastname: Kindermann
mesh_terms: D000818:Animals; D019605:Euryarchaeota / Q000378:metabolism; D008697:Methane / Q000737:chemistry*; D062105:Molecular Docking Simulation; D010088:Oxidoreductases / Q000737:chemistry; D012417:Rumen / Q000378:metabolism; D012418:Ruminants / Q000378:metabolism
chemical_list: D010088:Oxidoreductases; D008697:Methane
keywords: climate change; enteric methane; greenhouse gas; methanogenesis; methyl-coenzyme M reductase