title: AmtB is necessary for NH(4)(+)-induced nitrogenase switch-off and ADP-ribosylation in Rhodobacter capsulatus.
abstract: Rhodobacter capsulatus possesses two genes potentially coding for ammonia transporters, amtB and amtY. In order to better understand their role in the physiology of this bacterium and their possible significance in nitrogen fixation, we created single-knockout mutants. Strains mutated in either amtB or amtY did not show a growth defect under any condition tested and were still capable of taking up ammonia at nearly wild-type rates, but an amtB mutant was no longer capable of transporting methylamine. The amtB strain but not the amtY strain was also totally defective in carrying out ADP-ribosylation of Fe-protein or the switch-off of in vivo nitrogenase activity in response to NH(4)(+) addition. ADP-ribosylation in response to darkness was unaffected in amtB and amtBY strains, and glutamine synthetase activity was normally regulated in these strains in response to ammonium addition, suggesting that one role of AmtB is to function as an ammonia sensor for the processes that regulate nitrogenase activity.
authors.affiliation: Département de Microbiologie et Immunologie, Université de Montréal, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors.forename: Alexander F
authors.initials: AF
authors.lastname: Yakunin
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Hallenbeck
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000641:Ammonia; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008744:Methylamines / Q000378:metabolism; D009154:Mutation; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism*; D019159:Nonheme Iron Proteins / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: C098742:(methyl)ammonium uptake carrier, Corynebacterium; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D008744:Methylamines; D019159:Nonheme Iron Proteins; D000244:Adenosine Diphosphate; D000641:Ammonia; C027451:methylamine; D009591:Nitrogenase; D005974:Glutamate-Ammonia Ligase