Linked Life Data

10029518

Source:http://linkedlifedata.com/resource/pubmed/id/10029518

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1999-3-16
pubmed:abstractText
In the chemotaxis system of Escherichia coli, phosphorylation of the CheY protein plays an important role in regulating the swimming pattern of the cell. In vitro, CheY can be phosphorylated either by phosphotransfer from phospho-CheA or by acquiring a phosphoryl group from any of a variety of small, high-energy phosphodonor molecules such as acetyl phosphate. Previous work explored the rapid kinetics of CheY phosphorylation by CheA. Here we extend that work and examine the kinetics of CheY phosphorylation by several small-molecule phosphodonors, including acetyl phosphate, benzoyl phosphate, carbamoyl phosphate, 2-methoxybenzoyl phosphate, and phosphoramidate. Our results indicate that these phosphodonors bind to CheY with relatively low affinity (Ks values ranging from 10 to 600 mM) and that the rate constant (kphos) for phosphotransfer at saturating phosphodonor concentrations is relatively slow (values ranging from 0.05 to 0.5 s-1). By contrast, under identical conditions, phosphorylation of CheY by phospho-CheA occurs much more rapidly (kphos approximately 800 s-1) and reflects CheY binding to phospho-CheA considerably more tightly (Ks approximately 60 microM) than it does to the small-molecule phosphodonors. In comparing CheA-mediated phosphorylation of CheY to small-molecule-mediated phosphorylation of CheY, the large difference in kphos values suggests that phospho-CheA makes significant contributions to the catalysis of CheY phosphorylation. The effects of pH and ionic strength on CheY phosphorylation kinetics were also investigated. For CheA-->CheY phosphotransfer, increasing ionic strength resulted in increased Ks values while kphos was unaffected. For CheY phosphorylation by small-molecule phosphodonors, increasing ionic strength resulted in decreasing Ks values and increasing kphos values. The significance of these effects is discussed in relation to the catalytic mechanism of CheY phosphorylation by phospho-CheA and small-molecule phosphodonors.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
23
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2259-71
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Kinetic characterization of CheY phosphorylation reactions: comparison of P-CheA and small-molecule phosphodonors.
pubmed:affiliation
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park 20742, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.