title: The quaternary structure of Tet repressors bound to the Tn10-encoded tet gene control region determined by neutron solution scattering.
abstract: The spatial arrangement of Tet repressor dimer, both free and in complex with an 80 bp DNA fragment spanning the wild-type Tn10-encoded tet transcriptional control sequence containing a tandem repeat of two operators, has been determined by neutron small-angle scattering. The active, free Tet repressor dimer is an elongated and flat molecule with a maximum dimension of 11 +/- 1.5 mm which can be approximated by an ellipsoid with the half-axes 6 nm, 2.5 nm and 1 nm. The overall conformation undergoes no detectable change when the repressor dimer is bound to a DNA fragment containing a single tet operator. The normal distance between the centre of gravity of the protein and the DNA axis is 3.0 +/- 0.1 nm, indicating that the repressor dimer is mainly located on one side of the DNA. When bound to the wild type tet control DNA, the two repressor dimers have a centre-to-centre distance of 11.0 +/- 0.5 nm. Their minimal distance is 5 +/- 2 nm. Protein-protein contacts via loop formation of the DNA by repressor binding is excluded. The repressors are well separated and have no direct contact. A model is proposed where the two repressor dimers are located on opposite sides of the DNA and the DNA is not strongly bent in the complex.
authors.affiliation: Max-Planck-Institut für Biochemie, Martinsried, FRG.
authors.forename: H
authors.initials: H
authors.lastname: Lederer
authors.forename: K
authors.initials: K
authors.lastname: Tovar
authors.forename: G
authors.initials: G
authors.lastname: Baer
authors.forename: R P
authors.initials: RP
authors.lastname: May
authors.forename: W
authors.initials: W
authors.lastname: Hillen
authors.forename: H
authors.initials: H
authors.lastname: Heumann
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009502:Neutrons; D009875:Operator Regions, Genetic; D011487:Protein Conformation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012542:Scattering, Radiation; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004251:DNA Transposable Elements; D046911:Macromolecular Substances; D012097:Repressor Proteins; D014157:Transcription Factors; C034811:tetracycline resistance-encoding transposon repressor protein; D004247:DNA