title: Ammonia permeability of the soybean nodulin 26 channel.
abstract: Soybean nodulin 26 (nod26), a member of the aquaporin superfamily, is the major protein component of the symbiosome membrane that encloses nitrogen-fixing bacteroids in root nodules. Previous work has demonstrated that nod26 facilitates the transport of water and glycerol, although a potential additional role as a channel for fixed ammonia efflux has been hypothesized. In the present study it is shown that recombinant nod26 reconstituted into proteoliposomes facilitates NH(3) transport in an Hg(2+)-sensitive manner with a reduced activation energy, hallmarks of protein-facilitated transport characteristic of aquaporins. Comparison of the predicted single-channel transport rates of nod26 suggests a 4.9-fold preference for ammonia compared to water.
authors.affiliation: Graduate School of Genome Science and Technology, The University of Tennessee-Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
authors.forename: Jin Ha
authors.initials: JH
authors.lastname: Hwang
authors.forename: Sally R
authors.initials: SR
authors.lastname: Ellingson
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Roberts
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D003001:Cloning, Molecular; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008627:Mercuric Chloride / Q000494:pharmacology; D046529:Microscopy, Electron, Transmission; D010539:Permeability / Q000187:drug effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D008565:Membrane Proteins; D010940:Plant Proteins; D011510:Proteolipids; D011994:Recombinant Proteins; C045625:nodulin; C020485:proteoliposomes; D014867:Water; D008627:Mercuric Chloride; D000641:Ammonia