Linked Life Data

16701697

Source:http://linkedlifedata.com/resource/pubmed/id/16701697

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2006-6-12
pubmed:abstractText
Structural changes on LexA repressor promoted by acidic pH have been investigated. Intense protein aggregation occurred around pH 4.0 but was not detected at pH values lower than pH 3.5. The center of spectral mass of the Trp increased 400 cm(-1) at pH 2.5 relatively to pH 7.2, an indication that LexA has undergone structural reorganization but not denaturation. The Trp fluorescence polarization of LexA at pH 2.5 indicated that its hydrodynamic volume was larger than its dimer at pH 7.2. 4,4'-Dianilino-1,1'-binaphthyl-5,5'- disulfonic acid (bis-ANS) experiments suggested that the residues in the hydrophobic clefts already present at the LexA structure at neutral pH had higher affinity to it at pH 2.5. A 100 kDa band corresponding to a tetramer was obtained when LexA was subject to pore-limiting native polyacrylamide gel electrophoresis at this pH. The existence of this tetrameric state was also confirmed by small angle X-ray scattering (SAXS) analysis at pH 2.5. 1D 1H NMR experiments suggested that it was composed of a mixture of folded and unfolded regions. Although 14,000-fold less stable than the dimeric LexA, it showed a tetramer-monomer dissociation at pH 2.5 from the hydrostatic pressure and urea curves. Albeit with half of the affinity obtained at pH 7.2 (Kaff of 170 nM), tetrameric LexA remained capable of binding recA operator sequence at pH 2.5. Moreover, different from the absence of binding to the negative control polyGC at neutral pH, LexA bound to this sequence with a Kaff value of 1415 nM at pH 2.5. A binding stoichiometry experiment at both pH 7.2 and pH 2.5 showed a [monomeric LexA]/[recA operator] ratio of 2:1. These results are discussed in relation to the activation of the Escherichia coli SOS regulon in response to environmental conditions resulting in acidic intracellular pH. Furthermore, oligomerization of LexA is proposed to be a possible regulation mechanism of this regulon.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
16
pubmed:volume
359
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1059-74
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:16701697-Anilino Naphthalenesulfonates, pubmed-meshheading:16701697-Bacterial Proteins, pubmed-meshheading:16701697-Circular Dichroism, pubmed-meshheading:16701697-DNA, Bacterial, pubmed-meshheading:16701697-Dimerization, pubmed-meshheading:16701697-Escherichia coli, pubmed-meshheading:16701697-Gene Expression Regulation, Bacterial, pubmed-meshheading:16701697-Hydrogen-Ion Concentration, pubmed-meshheading:16701697-Magnetic Resonance Spectroscopy, pubmed-meshheading:16701697-Protein Conformation, pubmed-meshheading:16701697-Repressor Proteins, pubmed-meshheading:16701697-SOS Response (Genetics), pubmed-meshheading:16701697-Scattering, Radiation, pubmed-meshheading:16701697-Serine Endopeptidases, pubmed-meshheading:16701697-Solutions, pubmed-meshheading:16701697-Thermodynamics, pubmed-meshheading:16701697-X-Rays
pubmed:year
2006
pubmed:articleTitle
Tetramerization of the LexA repressor in solution: implications for gene regulation of the E.coli SOS system at acidic pH.
pubmed:affiliation
Laboratório de Genômica Estrutural, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590, Rio de Janerio, RJ, Brazil.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't