Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1993-8-19
pubmed:abstractText
The NTRC protein of enteric bacteria is an enhancer-binding protein that activates transcription by the sigma 54-holoenzyme form of RNA polymerase under nitrogen-limiting conditions. In vitro NTRC must be phosphorylated to catalyze ATP hydrolysis and activate transcription. The site of phosphorylation of NTRC from Salmonella typhimurium is Aspartate 54, which lies in the amino-terminal regulatory domain of the protein. We used site-directed mutagenesis to make "conservative" substitutions at residue 54 to alanine, asparagine, and glutamate, and examined the properties of the mutant NTRC proteins in vitro and in vivo. In vitro none of them was detectably phosphorylated, as expected if D54 is, in fact, the sole site of phosphorylation. D54A and D54N did not activate transcription of glnA but, interestingly, D54E activated constitutively. Activation by D54E was partial compared to that by phosphorylated wild-type NTRC. Combining D54A or D54N with S160F, a change in the central domain of NTRC that partially bypasses the requirement for phosphorylation, yielded doubly mutant proteins that were as active as a form carrying S160F alone, indicating that the changes in D54 did not adversely affect the function of the remainder of NTRC. Combining D54E with S160F increased the levels of constitutive ATPase activity and transcriptional activation above those of mutant NTRC proteins carrying either single change alone. We conclude that phosphorylation of aspartate 54 is required to activate NTRC and postulate that the D54E mutation mimics phosphorylation, thereby allowing NTRC to hydrolyze ATP and activate transcription. Phenotypes of mutant strains encoding NTRC proteins with substitutions at D54 indicated that phosphorylation of NTRC at position 54 was necessary for normal growth in the absence of glutamine and that such phosphorylation occurred to some extent even in the absence of NTRB.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
232
pubmed:geneSymbol
ntrC
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
67-78
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed-meshheading:8331671-Aspartic Acid, pubmed-meshheading:8331671-Bacterial Proteins, pubmed-meshheading:8331671-Base Sequence, pubmed-meshheading:8331671-DNA-Binding Proteins, pubmed-meshheading:8331671-Enhancer Elements, Genetic, pubmed-meshheading:8331671-Gene Expression Regulation, Bacterial, pubmed-meshheading:8331671-Glutamates, pubmed-meshheading:8331671-Molecular Sequence Data, pubmed-meshheading:8331671-Oligodeoxyribonucleotides, pubmed-meshheading:8331671-PII Nitrogen Regulatory Proteins, pubmed-meshheading:8331671-Phenotype, pubmed-meshheading:8331671-Phosphoproteins, pubmed-meshheading:8331671-Phosphorylation, pubmed-meshheading:8331671-Promoter Regions, Genetic, pubmed-meshheading:8331671-Protein Structure, Secondary, pubmed-meshheading:8331671-Salmonella typhimurium, pubmed-meshheading:8331671-Structure-Activity Relationship, pubmed-meshheading:8331671-Trans-Activators, pubmed-meshheading:8331671-Transcription, Genetic, pubmed-meshheading:8331671-Transcription Factors, pubmed-meshheading:8331671-Transcriptional Activation
pubmed:year
1993
pubmed:articleTitle
Glutamate at the site of phosphorylation of nitrogen-regulatory protein NTRC mimics aspartyl-phosphate and activates the protein.
pubmed:affiliation
Department of Plant Pathology, University of California, Berkeley 94720.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.