The solution structures of the trp-repressor from Escherichia coli in both the liganded (holo-) and unliganded (apo-) form, have been refined by restrained molecular dynamics with simulated annealing using the program XPLOR and additional experimental constraints. The ensemble of refined holorepressor structures have a root-mean-square deviation (r.m.s.d.) of 0.8 A relative to the average structure for the backbone of the dimer core (helices A, B, C, A', B', C') and 2.5 A for the helix-turn-helix DNA-binding domain (helices D and E). The corresponding values for the aporepressor are 0.9 A for the backbone of the ABC-dimer core and 3.2 A for the DE helix-turn-helix. The r.m.s.d. of the average structures from the corresponding crystal structures are 2.3 A for the holorepressor ABC core and 4.2 A for its DE region; 2.3 A for the aporepressor core and 5.5 A for its DE region. The relative disorder of the DNA-binding domain is reflected in a number of experimental parameters including substantially more rapid backbone proton exchange rates, exchange-limited relaxation times and crystallographic B-factors. The stabilizing effect of the L-Trp ligand is evident in these measurements, as it is in the higher precision of the holorepressor structure.
PDB ID: 1WRSDownload
MMDB ID: 51929
PDB Deposition Date: 1995/5/12
Updated in MMDB: 2012/11
Experimental Method:
solution nmr
Source Organism:
Similar Structures:
Molecular Components in 1WRS
Label Count Molecule
Proteins (2 molecules)
Holo TRP Repressor(Gene symbol: trpR)
Molecule annotation
Chemicals (2 molecules)
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