3ssx
E. coli trp aporeporessor L75F mutantE. coli trp aporeporessor L75F mutant
Structural highlights
Function[TRPR_ECOLI] This protein is an aporepressor. When complexed with L-tryptophan it binds the operator region of the trp operon (5'-ACTAGT-'3') and prevents the initiation of transcription. The complex also regulates trp repressor biosynthesis by binding to its regulatory region. Publication Abstract from PubMedExtensive environment-dependent rearrangement of the helix-turn-helix DNA recognition region and adjacent L-tryptophan binding pocket is reported in the crystal structure of dimeric E. coli trp aporepressor with point mutation Leu75Phe. In one of two subunits, the eight residues immediately C-terminal to the mutation are shifted forward in helical register by three positions, and the five following residues form an extrahelical loop accommodating the register shift. In contrast, the second subunit has wildtype-like conformation, as do both subunits in an isomorphous wildtype control structure. Treated together as an ensemble pair, the distorted and wildtype-like conformations agree more fully than either conformation alone with previously reported NOE measurements on the mutant apoprotein, and account more completely for its diverse biochemical and biophysical properties. The register-shifted segment Ile79-Ala80-Thr81-Ile82-Thr83 is helical in both conformations despite low helical propensity, suggesting an important structural role for the steric constraints imposed by beta-branched residues in helical conformation. Environment-dependent long-range structural distortion in a temperature-sensitive point mutant.,Carey J, Benoff B, Harish B, Yuan L, Lawson CL Protein Sci. 2011 Nov 4. doi: 10.1002/pro.759. PMID:22057811[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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