title: Channel-mediated permeation of ammonia gas through the peribacteroid membrane of soybean nodules.
abstract: Ammonia permeability of the peribacteroid membrane (PBM) from N(2)-fixing soybean nodules was measured (8x10(-5) m/s) using isolated PBM in a stopped-flow spectrofluorimeter. Ammonia (NH(3)) uptake into PBM vesicles was inhibited by up to 42% by HgCl(2) (EC(50)=2.9 microM, mercaptoethanol-reversible) and reduced by ATP pre-incubation. The activation energy of NH(3) uptake (52 kJ/mol) increased (118 kJ/mol) with HgCl(2). Water transport was also HgCl(2)-sensitive (EC(50)=52.6 microM), but increased by ATP pre-incubation. NH(3) and H(2)O may permeate via different pathways through Nodulin 26 or there is another protein on the PBM that is permeable to NH(3).
authors.affiliation: School of Biological Sciences, The Flinders University of South Australia, G.P.O. Box 2100, Adelaide, S.A., Australia.
authors.forename: C M
authors.initials: CM
authors.lastname: Niemietz
authors.forename: S D
authors.initials: SD
authors.lastname: Tyerman
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008627:Mercuric Chloride / Q000378:metabolism; D010539:Permeability; D013025:Glycine max / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D007473:Ion Channels; D014867:Water; D008627:Mercuric Chloride; D000641:Ammonia