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The quaternary structure of Tet repressors bound to the Tn10‐encoded tet gene control region determined by neutron solution scattering.
Author(s) -
Lederer H.,
Tovar K.,
Baer G.,
May R. P.,
Hillen W.,
Heumann H.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb03499.x
Subject(s) - biology , repressor , gene , tn10 , genetics , microbiology and biotechnology , gene expression , genome , transposable element
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.