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A sensor protein involved in induction of nitrate assimilation in Azotobacter chroococcum
Author(s) -
Muñoz-Centeno María C.,
Peciña Ana,
Cejudo Francisco J.,
Paneque Antonio
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00843-5
Subject(s) - azotobacter chroococcum , assimilation (phonology) , nitrogen assimilation , chemistry , nitrate , biochemistry , botany , biology , organic chemistry , genetics , bacteria , linguistics , philosophy
Nitrogen‐fixing Azotobacter chroococcum cells, but not ammonium‐ or nitrate‐grown cells, exhibited two polypeptide components of 22 and 35 kDa, respectively, that we termed P22 and P35. Bidimensional polyacrylamide gel electrophoresis analysis of preparations from N 2 ‐fixing cells that had been transferred to nitrate medium and then incubated for 2 h revealed that P22 had shifted to a more acidic part of the gel while P35 did not change its electrophoretic pattern. Using [ 32 P]orthophosphoric acid it could be demonstrated that the shift in mobility of P22 was due to the phosphorylation of the polypeptide dependent on nitrate (nitrite). The A. chroococcum TR1 strain, which is unable to use nitrate as a nitrogen source and displays activities of nitrogenase, nitrate reductase and nitrite reductase, exhibited both polypeptides. In contrast, P22 and P35 were absent from A. chroococcum MCD1, a mutant strain that cannot assimilate nitrate and lacks the nitrate‐reducing enzymatic system. The results suggest that P22 could act as a sensor protein for nitrate in A. chroococcum .