title: An engineered intersubunit disulfide enhances the stability and DNA binding of the N-terminal domain of lambda repressor.
abstract: Site-directed mutagenesis has been used to replace Tyr-88 at the dimer interface of the N-terminal domain of lambda repressor with cysteine. Computer model building had suggested that this substitution would allow formation of an intersubunit disulfide without disruption of the dimer structure [Pabo, C. O., & Suchanek, E. G. (1986) Biochemistry (preceding paper in this issue)]. We find that the Cys-88 protein forms a disulfide-bonded dimer that is very stable to reduction by dithiothreitol and has increased operator DNA binding activity. The covalent Cys88-Cys88' dimer is also considerably more stable than the wild-type protein to thermal denaturation or urea denaturation. As a control, Tyr-85 was replaced with cysteine. A Cys85-Cys85' disulfide cannot form without disrupting the wild-type structure, and we find that this disulfide bond reduces the DNA binding activity and stability of the N-terminal domain.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002942:Circular Dichroism; D003198:Computer Simulation; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D007700:Kinetics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011487:Protein Conformation; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014508:Urea / Q000494:pharmacology; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D014508:Urea; D004247:DNA