2TCT

THE COMPLEX FORMED BETWEEN TET REPRESSOR AND TETRACYCLINE-MG2+ REVEALS MECHANISM OF ANTIBIOTIC RESISTANCE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Work: 0.180 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

The complex formed between Tet repressor and tetracycline-Mg2+ reveals mechanism of antibiotic resistance.

Kisker, C.Hinrichs, W.Tovar, K.Hillen, W.Saenger, W.

(1995) J.Mol.Biol. 247: 260-280

  • Also Cited By: 2XB5

  • PubMed Abstract: 
  • In recent years Gram-negative bacteria have developed several resistance mechanisms against the broad-spectrum antibiotic tetracycline (Tc). The most abundant mechanism involves a membrane-associated protein (TetA) that exports the antibiotic out of ...

    In recent years Gram-negative bacteria have developed several resistance mechanisms against the broad-spectrum antibiotic tetracycline (Tc). The most abundant mechanism involves a membrane-associated protein (TetA) that exports the antibiotic out of the bacterial cell before it can attach to the ribosomes and inhibit polypeptide elongation. The expression of the TetA protein is regulated by the Tet repressor (TetR). It occurs as a homodimer and binds with two alpha-helix-turn-alpha-helix motifs (HTH) to two tandemly orientated DNA operators, thereby blocking the expression of the associated genes, one encoding for TetA and the other for TetR. If Tc in complex with a divalent cation binds to TetR, a conformational change occurs and the induced TetR is then unable to bind to DNA. TetR of class D, TEtRD, was cocrystallized with tetracycline (7HTc) and Mg2+ in space group I4(1)22 and studied by X-ray diffraction. One TetRD monomer occupies the crystal asymmetric unit, and the dimer is formed by a crystallographic 2-fold rotation. The crystal structure was determined by multiple isomorphous replacement at 2.5 A resolution, and on this basis the structure of the nearly isomorphous complex with 7-chlorotetracycline, TetRD/(Mg 7CITc)+, has been refined to an R-factor of 18.3% using all reflections to 2.1 A resolution. TetRD folds into ten alpha-helices with connecting turns and loops. The N-terminal three alpha-helices of the repressor form the DNA-binding domain, including the HTH with an inverse orientation compared with HTH in other DNA-binding proteins. The distance of 39 A between the two recognition helices explains the inability of the induced TetR to bind to B-form DNA. The core of the protein is formed by helices alpha 5 to alpha 10. It is responsible for dimerization and contains, for each monomer, a binding pocket that accommodates Tc in the presence of a divalent cation. The structure of the TetRD/(Mg 7CITc)+ complex reveals the octahedral coordination of Mg2+ by Tc (chelating O-11, and O-12), His100 N epsilon and by three water molecules; in addition there is an extended network of hydrogen bonding and van der Waals interactions formed between 7CITc and TetR. The detailed view of the Tc-binding pocket and the interactions between the antibiotic and the repressor offers the first solid basis for rational tetracycline design, with the aim of circumventing resistance.


    Related Citations: 
    • Structure of the Tet Repressor-Tetracycline Complex and Regulation of Antibiotic Resistance
      Hinrichs, W.,Kisker, C.,Duevel, M.,Mueller, A.,Tovar, K.,Hillen, W.,Saenger, W.
      (1994) Science 264: 418


    Organizational Affiliation

    Institut für Kristallographie, Freie Universität Berlin, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
TETRACYCLINE REPRESSOR
A
207Escherichia coliMutation(s): 0 
Gene Names: tetR
Find proteins for P0ACT4 (Escherichia coli)
Go to UniProtKB:  P0ACT4
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MG
Query on MG

Download SDF File 
Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
CTC
Query on CTC

Download SDF File 
Download CCD File 
A
7-CHLOROTETRACYCLINE
C22 H23 Cl N2 O8
CYDMQBQPVICBEU-XRNKAMNCSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
CTCKa: ~10000000 M-1 BINDINGMOAD
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Work: 0.180 
  • Space Group: I 41 2 2
Unit Cell:
Length (Å)Angle (°)
a = 68.780α = 90.00
b = 68.780β = 90.00
c = 181.450γ = 90.00
Software Package:
Software NamePurpose
X-PLORrefinement
X-PLORphasing
X-PLORmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1996-04-03
    Type: Initial release
  • Version 1.1: 2008-03-25
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance
  • Version 1.3: 2017-11-29
    Type: Derived calculations, Other