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Phage phi29 transcription regulator p4-DNA complexPhage phi29 transcription regulator p4-DNA complex
Structural highlights
FunctionTF4_BPPH2 Mediates, together with protein p6, the early to late transcriptional switch by stabilizing the binding of host RNA polymerase (RNAP) to the late A3 promoter. Activates transcription from the late A3 promoter and represses the main early promoters A2b and A2c by modifying the topology of the sequences encompassing early promoters A2c and A2b and late promoter A3 in a hairpin. Proteins p6 and p4 bind cooperatively to an approximately 200 bp DNA region located between the late A3 and the early A2c promoters. Binding of p4 molecules induces the reorganization of the binding of protein p6, giving rise to the nucleoprotein complex responsible for the switch from early to late transcription.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedProtein p4 affects the transcriptional switch that divides bacteriophage phi29 infection in early and late phases. The synthesis of DNA replication proteins and p4 takes place in the early phase, while structural, morphogenesis, and lysis proteins are synthesized in the late phase. Transcriptional switch by p4 is achieved by activating the late promoter A3 and repressing the early promoters A2b and A2c. The crystal structure of p4 alone and in complex with a 41 bp DNA, including the A3 promoter binding site, helps us to understand how the phage cycle is controlled. Protein p4 has a unique alpha/beta fold that includes a DNA recognition motif consisting of two N-terminal beta turn substructures, or N-hooks, located at the tips of an elongated protein homodimer. The two N-hooks enter the major groove of the double helix, establishing base-specific contacts. A high DNA curvature allows p4 N-hooks to reach two major groove areas three helical turns apart, like a bow and its string. The structure of phage phi29 transcription regulator p4-DNA complex reveals an N-hook motif for DNA.,Badia D, Camacho A, Perez-Lago L, Escandon C, Salas M, Coll M Mol Cell. 2006 Apr 7;22(1):73-81. PMID:16600871[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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