title: Mutant tryptophan aporepressors with altered specificities of corepressor recognition.
abstract: The Escherichia coli trpR gene encodes tryptophan aporepressor, which binds the corepressor ligand, L-tryptophan, to form an active repressor complex. The side chain of residue valine 58 of Trp aporepressor sits at the bottom of the corepressor (L-tryptophan) binding pocket. Mutant trpR genes encoding changes of Val58 to the other 19 naturally occurring amino acids were made. Each of the mutant proteins requires a higher intracellular concentration of tryptophan for activation of DNA binding than wild-type aporepressor. Whereas wild-type aporepressor is activated better by 5-methyltryptophan (5-MT) than by tryptophan, Ile58 and other mutant aporepressors prefer tryptophan to 5-MT as corepressor, and Ala58 and Gly58 prefer 5-MT much more strongly than wild-type aporepressor in vivo. These mutant aporepressors are the first examples of DNA-binding proteins with altered specificities of cofactor recognition.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles 90089.
authors.forename: D N
authors.initials: DN
authors.lastname: Arvidson
authors.forename: M
authors.initials: M
authors.lastname: Shapiro
authors.forename: P
authors.initials: P
authors.lastname: Youderian
mesh_terms: D001059:Apoproteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism*; D014633:Valine / Q000737:chemistry
chemical_list: D001059:Apoproteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; C027190:TRPR protein, E coli; D014364:Tryptophan; D014633:Valine