Linked Life Data

16442736

Source:http://linkedlifedata.com/resource/pubmed/id/16442736

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2006-3-6
pubmed:abstractText
Most cyanobacteria take up nitrate or nitrite through a multisubunit ABC transporter (ATP-binding cassette) located in the cytoplasmic membrane. Nitrate and nitrite transport activity is instantaneously blocked by the presence of ammonium in the medium. Previous biochemical studies reported the existence of phosphorylation/dephosphorylation events of the nitrate transporter (NRT) related to the presence of ammonium-sensitive kinase/phosphatase activities in plasma membranes of the cyanobacterium Synechococcus elongatus PCC 6301. In this work, we have analyzed the biochemical properties of the periplasmic nitrate/nitrite-binding subunit (NrtA) of NRT from the thermophilic nondiazotrophic cyanobacterium Phormidium laminosum. Our results show that cyanobacterial NrtA is phosphorylated in vivo. However, substrate binding activity in vitro is not affected by the phosphorylation state of the protein, ruling out the possibility that phosphorylation/dephosphorylation of NrtA is involved in the regulation of the nitrate/nitrite uptake by NRT transporter. Moreover, NrtA is present as multiple isoforms showing the same molecular mass but different isoelectric points ranging from pI 5 to 6. Mass spectrometric characterization of NrtA isoforms shows that the protein is phosphorylated at residue Tyr203, and contains several methionine sulphoxide residues which account for the observed isoforms. Both phosphorylated and non-phosphorylated forms of NrtA are active in vitro, showing comparable binding affinity for nitrate and nitrite. Both substrates behave as pure competitive inhibitors with a binding stoichiometry of one molecule of anion per NrtA monomer.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:volume
1760
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
172-81
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:16442736-ATP-Binding Cassette Transporters, pubmed-meshheading:16442736-Amino Acid Sequence, pubmed-meshheading:16442736-Anion Transport Proteins, pubmed-meshheading:16442736-Binding, Competitive, pubmed-meshheading:16442736-Cyanobacteria, pubmed-meshheading:16442736-Electrophoresis, Polyacrylamide Gel, pubmed-meshheading:16442736-Isoelectric Point, pubmed-meshheading:16442736-Kinetics, pubmed-meshheading:16442736-Mass Spectrometry, pubmed-meshheading:16442736-Molecular Sequence Data, pubmed-meshheading:16442736-Nitrates, pubmed-meshheading:16442736-Nitrites, pubmed-meshheading:16442736-Phosphorylation, pubmed-meshheading:16442736-Protein Binding, pubmed-meshheading:16442736-Protein Isoforms, pubmed-meshheading:16442736-Spectrometry, Mass, Matrix-Assisted Laser..., pubmed-meshheading:16442736-Tyrosine
pubmed:year
2006
pubmed:articleTitle
The nitrate/nitrite ABC transporter of Phormidium laminosum: phosphorylation state of NrtA is not involved in its substrate binding activity.
pubmed:affiliation
Enzyme and Cell Technology Group, Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, University of the Basque Country, P.O. Box 644, E-48080 Bilbao, Spain.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't