Involvement of the ammonium transporter AmtB in nitrogenase regulation and ammonium excretion in Pseudomonas stutzeri A1501.
The nitrogen-fixing Pseudomonas stutzeri strain A1501 contains two ammonium transporter genes, amtB1 and amtB2, linked to glnK. Growth of an amtB1-amtB2 double deletion mutant strain was not impaired compared to that of the wild type under any conditions tested, and it was still capable of taking up ammonium ions at nearly wild-type rates. Nitrogenase activity was repressed in wild-type strain A1501 in response to the addition of ammonium, but nitrogenase activity was only partially impaired in the amtB1 and amtB2 double mutant, suggesting that the two AmtB proteins are involved in regulating expression of nitrogenase or its activity in response to ammonium. An interaction between GlnK and AmtB1 or AmtB2 was observed in a yeast two-hybrid assay. Ammonium was excreted by the amtB double mutant strain under nitrogen fixation conditions, particularly when nifA was expressed constitutively. This suggests that AmtB proteins play a role in controlling the internal pool of ammonia within the cell.
School of Life Science, Northeast Agricultural University, Harbin 150030, China. jerrity@163.com
Tao
T
Zhang
Yongliang
Y
Yan
Sheng
S
He
Shuzhen
S
Ping
Khandakar Mohiul
KM
Alam
Yunlei
Y
Han
Xiaodong
X
Liu
Wei
W
Lu
Wei
W
Zhang
Ming
M
Chen
Wensheng
W
Xiang
Xiangjing
X
Wang
Min
M
Lin
D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D009591:Nitrogenase / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D044223:Pseudomonas stutzeri / Q000235:genetics / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D027682:Cation Transport Proteins; D000644:Quaternary Ammonium Compounds; D009591:Nitrogenase