1- Crystal of the TetR classD homodimer bound to the DNA operator
TetR is an homodimer.
TetR homodimer is constituted by two identical monomers related by a twofold rotation axis coinciding with the long dimension of the dimer.The monomer A iscoulored in red and the monomer A' in blue. Each monomer folds into ten alpha-helices.
Place the pointer in the figure over the helix of the red monomer that you wish to identify.
The homodimer contains two DNA-binding domains and a regulatory core domain involved in dimerization and inducer binding.
Each DNA-binding domain is located in the N-terminal fragment of each monomer.
The DNA-binding domain is constituted by the helices alpha 1, alpha 2 and alpha 3.
The helix alpha 4 connect this domain with the regulatory domain.
The helices alpha 5 to alpha 10 and their symmetric counterparts alpha 5’ and alpha 10’ form the regulatory domain.
The regulatory domain is responsible for dimerization and contains, for each monomer, a binding pocket that accommodates Tc in the presence of a divalent cation.
TetR is an homodimer.
The helices alpha 5, alpha 8 and alpha 10 and their counterparts alpha 5’, alpha 8’ and alpha 10’ constitute the scaffold of the regulatory core domain and their structure is the most conserved in both TetR conformations.
The antiparallel helices alpha 8 and alpha 10 crosses the helices alpha 8’ and alpha 10’ at and angle of 50º drawing two “X” in different planes. This “double X motif” constitutes the dimerization interface.
The Tc binding-pocket is a cavity formed by:
• Outer wall: alpha 7
• Inner wall: alpha 5 and alpha 8
• Floor: alpha 6 and the C-terminal extreme of alpha 4
• Ceiling: the extremes of alpha 7 and alpha 8 with the interconnecting loop.
• Entrance: alpha 9’ and the C-terminal extreme of alpha 8’ and the loop that connects both.
• Exit : loop 4-5.
The figures were prepared with WebLab Viewer (Molecular Simulations Inc.)
