Linked Life Data

18395746

Source:http://linkedlifedata.com/resource/pubmed/id/18395746

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2008-4-21
pubmed:databankReference
pubmed:abstractText
The Tet repressor (TetR) mediates the most important mechanism of bacterial resistance against tetracycline (Tc) antibiotics. In the absence of Tc, TetR is tightly bound to its operator DNA; upon binding of Tc with an associated Mg(2+) ion, it dissociates from the DNA, allowing expression of the repressed genes. Its tight control by Tc makes TetR broadly useful in genetic engineering. The Tc binding site is over 20 A from the DNA, so the binding signal must propagate a long distance. We use molecular dynamics simulations and continuum electrostatic calculations to test two models of the allosteric mechanism. We simulate the TetR:DNA complex, the Tc-bound, "induced" TetR, and the transition pathway between them. The simulations support the model inferred previously from the crystal structures and reveal new details. When [Tc:Mg](+) binds, the Mg(2+) ion makes direct and water-mediated interactions with helix 8 of one TetR monomer and helix 6 of the other monomer, and helix 6 is pulled in towards the central core of the structure. Hydrophobic interactions with helix 6 then pull helix 4 in a pendulum motion, with a maximal displacement at its N-terminus: the DNA interface. The crystal structure of an additional TetR reported here corroborates this motion. The N-terminal residue of helix 4, Lys48, is highly conserved in DNA-binding regulatory proteins of the TetR class and makes the largest contribution of any amino acid to the TetR:DNA binding free energy. Thus, the conformational changes lead to a drastic reduction in the TetR:DNA binding affinity, allowing TetR to detach itself from the DNA. Tc plays the role of a specific Mg(2+) carrier, whereas the Mg(2+) ion itself makes key interactions that trigger the allosteric transition in the TetR:Tc complex.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
1089-8638
pubmed:author
pubmed:issnType
Electronic
pubmed:day
9
pubmed:volume
378
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
898-912
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
2008
pubmed:articleTitle
Tet repressor induction by tetracycline: a molecular dynamics, continuum electrostatics, and crystallographic study.
pubmed:affiliation
Laboratoire de Biochimie (CNRS UMR7654), Department of Biology, Ecole Polytechnique, 91128 Palaiseau, France.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't