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A role for the signal transduction protein P II in the control of nitrate/nitrite uptake in a cyanobacterium
Author(s) -
Lee Hyun-Mi,
Flores Enrique,
Herrero Antonia,
Houmard Jean,
Tandeau de Marsac Nicole
Publication year - 1998
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/s0014-5793(98)00451-7
Subject(s) - nitrite , mutant , nitrate , operon , wild type , ammonium , biochemistry , nitrite reductase , chemistry , biology , strain (injury) , synechococcus , gene , cyanobacteria , bacteria , genetics , organic chemistry , anatomy
In the cyanobacterium Synechococcus sp. strain PCC 7942, ammonium exerts a rapid and reversible inhibition of the nitrate and nitrite uptake, and the P II protein (GlnB) is differentially phosphorylated depending on the intracellular N/C balance. RNA/DNA hybridizations, as well as nitrate and nitrite uptake experiments, were carried out with the wild‐type strain and a P II ‐null mutant. The transcriptional control by ammonium of the expression of the nir ‐ nrtABCD‐narB operon remained operative in the mutant but, in contrast to the wild‐type strain, the mutant took up nitrate and nitrite even in the presence of ammonium. Moreover, the wild‐type phenotype was restored by insertion of a copy of the wild‐type glnB gene in the genome of the P II ‐null mutant. These results indicate that the unphosphorylated form of P II is involved in the short‐term inhibition by ammonium of the nitrate and nitrite uptake in Synechococcus sp. strain PCC 7942.