Structure of a Ternary Transcription Activation Complex

• Published in: Molecular cell 2004-01, Vol.13 (1), p.45-53
• Main Authors: Jain, Deepti, Nickels, Bryce E., Sun, Li, Hochschild, Ann, Darst, Seth A.
• Format: Article
• Language: English
• Subjects: AcI protein; Amino Acid Sequence; Bacteriophage lambda - genetics; Base Sequence; cI protein; Consensus Sequence; Crystallography, X-Ray; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; DNA-Directed RNA Polymerases - chemistry; DNA-Directed RNA Polymerases - genetics; DNA-Directed RNA Polymerases - metabolism; Escherichia coli - genetics; Holoenzymes - chemistry; Holoenzymes - metabolism; Hydrogen Bonding; Models, Molecular; Molecular Sequence Data; Phage ^l; Promoter Regions, Genetic; Protein Binding; Sigma Factor - chemistry; Sigma Factor - genetics; Sigma Factor - metabolism; Transcription, Genetic; Transcriptional Activation
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/S1097-2765(03)00483-0

The cI protein of bacteriophage λ (λcI) activates transcription by binding a DNA operator just upstream of the promoter and interacting with the RNA polymerase σ subunit domain 4 (σ 4). We determined the crystal structure of the λcI/σ 4/DNA ternary complex at 2.3 Å resolution. There are no conformational changes in either protein, which interact through an extremely small interface involving at most 6 amino acid residues. The interactions of the two proteins stabilize the binding of each protein to the DNA. The results provide insight into how activators can operate through a simple cooperative binding mechanism but affect different steps of the transcription initiation process.