Linked Life Data

2404975

Source:http://linkedlifedata.com/resource/pubmed/id/2404975

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1990-3-7
pubmed:abstractText
Enzyme I is the first protein of the phospho transfer sequence in the bacterial phosphoenolpyruvate:glycose phosphotransferase system. This protein exhibits a temperature-dependent monomer/dimer equilibrium. The nucleotide sequence of Escherichia coli ptsI indicates four -SH residues per subunit (Saffen, D. W., Presper, K. A., Doering, T. L., and Roseman, S. (1987) J. Biol. Chem. 262, 16241-16253). In the present experiments, the sulfhydryl groups of the E. coli enzyme were studied with various -SH-specific reagents. Titration of Enzyme I with 5,5'-dithiobis-2-nitrobenzoic acid also revealed four reacting -SH groups. The kinetics of the 5,5'-dithiobis-2-nitrobenzoic acid reaction with Enzyme I exhibit biphasic character, with pseudo-first order rate constants of 2.3 x 10(-2)/s and 2.3 x 10(-3)/s at pH 7.5, at room temperature. Fractional amplitudes associated with the rate constants were 25 +/- 5% for the fast and 75 +/- 5% for the slow rate. The "slow" rate was influenced by ligands that react with Enzyme I (the protein HPr, Mg2+, Mg2+ plus P-enolpyruvate), and also by temperature (at the temperature range where the monomer/dimer association occurs). The fractional ratio of the two rates remained at 1:3 under these conditions. Thus, under all conditions tested, two classes of -SH groups were detected, one reacting more rapidly than the other three -SH groups. Modification of the "fast" -SH group results in an active enzyme capable of forming dimer, whereas modification of the slow -SH groups results in inactive and monomeric Enzyme I. The enzyme was labeled with pyrene maleimide under conditions where only the more reactive sulfhydryl group was derivatized. Hydrolysis by trypsin followed by reverse-phase high performance liquid chromatography analysis of the peptide mixture resulted in only one fluorescent peak. This peak was not observed when the more reactive sulfhydryl residue was protected prior to pyrene maleimide labeling. Amino acid sequencing of the fluorescent peak indicated that the more reactive residue is the C-terminal amino acid residue, cysteine 575. The results provide a means for selectively labeling Enzyme I with a fluorophore at a single site while retaining full catalytic activity.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
265
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1985-95
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:2404975-Amino Acid Sequence, pubmed-meshheading:2404975-Binding Sites, pubmed-meshheading:2404975-Chromatography, High Pressure Liquid, pubmed-meshheading:2404975-Dithionitrobenzoic Acid, pubmed-meshheading:2404975-Escherichia coli, pubmed-meshheading:2404975-Kinetics, pubmed-meshheading:2404975-Molecular Sequence Data, pubmed-meshheading:2404975-Peptide Fragments, pubmed-meshheading:2404975-Peptide Mapping, pubmed-meshheading:2404975-Phosphoenolpyruvate Sugar Phosphotransferase System, pubmed-meshheading:2404975-Phosphorylation, pubmed-meshheading:2404975-Phosphotransferases (Nitrogenous Group Acceptor), pubmed-meshheading:2404975-Protein Binding, pubmed-meshheading:2404975-Pyrenes, pubmed-meshheading:2404975-Substrate Specificity, pubmed-meshheading:2404975-Sulfhydryl Compounds, pubmed-meshheading:2404975-Thermodynamics, pubmed-meshheading:2404975-Time Factors, pubmed-meshheading:2404975-Trypsin
pubmed:year
1990
pubmed:articleTitle
Sugar transport by the bacterial phosphotransferase system. Characterization of the sulfhydryl groups and site-specific labeling of enzyme I.
pubmed:affiliation
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.