The structural basis for the interaction between L-tryptophan and the Escherichia coli trp aporepressor

• Published in: The Journal of biological chemistry Vol. 262; no. 10; pp. 4922 - 4927
• Main Authors: Marmorstein, R.Q., Joachimiak, A., Sprinzl, M., Sigler, P.B.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05.04.1987; American Society for Biochemistry and Molecular Biology
• Subjects: Apoproteins - metabolism; Bacterial Proteins; Binding Sites; Binding, Competitive; Biological and medical sciences; Escherichia coli; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Molecular and cellular biology; Molecular genetics; Repressor Proteins - metabolism; Stereoisomerism; Structure-Activity Relationship; Transcription Factors - metabolism; Transcription. Transcription factor. Splicing. Rna processing; Tryptophan - analogs & derivatives; Tryptophan - metabolism; Aminoacid; Escherichia coli; Tryptophan; Bacteria; Molecular interaction; Transcription repressor; Stereochemistry; Escherichieae; Equilibrium dialysis; Enterobacteriaceae
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)61285-2

We have employed equilibrium dialysis to help study the mechanism by which the unliganded Escherichia coli trp aporepressor is activated by L-tryptophan to the liganded trp repressor. By measuring the relative affinity of L-tryptophan and various tryptophan analogues for the co-repressor's binding site, we have estimated the extent to which each of the functional groups of L-tryptophan contributes to the liganding process and discuss their role in the context of the crystal structures of the trp repressor and aporepressor. We have found that the indole ring and alpha carboxyl group of L-tryptophan are mainly responsible for its affinity to the aporepressor. The alpha amino group, however, has a small negative contribution to the affinity of L-tryptophan for the aporepressor which may be associated with its essential role in operator-specific binding.