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Homo-dimeric Trp repressor binds a DNA operator along with its co-repressor Tryptophan Trp repressor is a homo-dimer, colored red and blue. The helix-turn-helix motif in each monomer is colored pink or cyan. The co-repressor, tryptophan, is colored yellow. The Tryptophan is sandwiched between two Arg residues, one from the helix that contacts the DNA. In this way, Tryptophan binding helps to position the helices for proper DNA binding.The helix-turn-helix motif interacts with the bases of the DNA. Arg 69 of the repressor is shown in blue and a base pair of DNA is shown in white.
1tro (PDB) Crystal structure of trp repressor/operator complex at atomic resolution. |