Glutamine Synthetase Sensitivity to Oxidative Modification during Nutrient Starvation in Prochlorococcus marinus PCC 9511.
Glutamine synthetase plays a key role in nitrogen metabolism, thus the fine regulation of this enzyme in Prochlorococcus, which is especially important in the oligotrophic oceans where this marine cyanobacterium thrives. In this work, we studied the metal-catalyzed oxidation of glutamine synthetase in cultures of Prochlorococcus marinus strain PCC 9511 subjected to nutrient limitation. Nitrogen deprivation caused glutamine synthetase to be more sensitive to metal-catalyzed oxidation (a 36% increase compared to control, non starved samples). Nutrient starvation induced also a clear increase (three-fold in the case of nitrogen) in the concentration of carbonyl derivatives in cell extracts, which was also higher (22%) upon addition of the inhibitor of electron transport, DCMU, to cultures. Our results indicate that nutrient limitations, representative of the natural conditions in the Prochlorococcus habitat, affect the response of glutamine synthetase to oxidative inactivating systems. Implications of these results on the regulation of glutamine synthetase by oxidative alteration prior to degradation of the enzyme in Prochlorococcus are discussed.
Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, Universidad de Córdoba, Córdoba, Spain.
Guadalupe
G
Gómez-Baena
Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, Universidad de Córdoba, Córdoba, Spain.
María Agustina
MA
Domínguez-Martín
Department of Biological Sciences, The George Washington University, Washington, D.C., United States of America.
Robert P
RP
Donaldson
Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, Universidad de Córdoba, Córdoba, Spain.
José Manuel
JM
García-Fernández
Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, Universidad de Córdoba, Córdoba, Spain.
Jesús
J
Diez
D001426:Bacterial Proteins / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D010084:Oxidation-Reduction; D048929:Prochlorococcus / Q000201:enzymology*; D011499:Protein Processing, Post-Translational
D001426:Bacterial Proteins; D005974:Glutamate-Ammonia Ligase