Conformational changes of the Tet repressor induced by tetracycline trapping.
The X-ray crystal structure analysis of inducer-free Tet repressor, TetR, at 2.4 A resolution identifies one of two openings of the tunnel-like binding site as the entrance for the inducer tetracycline-Mg2+, [Mg Tc]+. Recognition and binding of the inducer unleashes conformational changes leading to the induced state of TetR. In the first step, the C-terminal turn of alpha-helix 6 unwinds, thereby altering the orientation of alpha-helix 4. This different orientation of alpha-helix 4 is stabilized by a series of hydrogen bonds mediated through a chain of eight water molecules. The alpha-helix 4 connects the DNA-binding domain (alpha-helices 1 to 3) to the rigid TetR core, and thus regulates gene expression through its respective orientations.
Orth
P
P
Institut für Kristallographie, Freie Universität Berlin, Germany.
Cordes
F
F
Schnappinger
D
D
Hillen
W
W
Saenger
W
W
Hinrichs
W
W
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics; D013752:Tetracycline / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C034811:tetracycline resistance-encoding transposon repressor protein; D014867:Water; D013752:Tetracycline