title: Crystal structure of the bacteriophage T4 late-transcription coactivator gp33 with the β-subunit flap domain of Escherichia coli RNA polymerase.
abstract: Activated transcription of the bacteriophage T4 late genes, which is coupled to concurrent DNA replication, is accomplished by an initiation complex containing the host RNA polymerase associated with two phage-encoded proteins, gp55 (the basal promoter specificity factor) and gp33 (the coactivator), as well as the DNA-mounted sliding-clamp processivity factor of the phage T4 replisome (gp45, the activator). We have determined the 3.0 Å-resolution X-ray crystal structure of gp33 complexed with its RNA polymerase binding determinant, the β-flap domain. Like domain 4 of the promoter specificity σ factor (σ(4)), gp33 interacts with RNA polymerase primarily by clamping onto the helix at the tip of the β-flap domain. Nevertheless, gp33 and σ(4) are not structurally related. The gp33/β-flap structure, combined with biochemical, biophysical, and structural information, allows us to generate a structural model of the T4 late promoter initiation complex. The model predicts protein/protein interactions within the complex that explain the presence of conserved patches of surface-exposed residues on gp33, and provides a structural framework for interpreting and designing future experiments to functionally characterize the complex.
authors.affiliation: Laboratory of Molecular Biophysics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
authors.forename: Kelly-Anne F
authors.initials: KA
authors.lastname: Twist
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Campbell
authors.forename: Padraig
authors.initials: P
authors.lastname: Deighan
authors.forename: Sergei
authors.initials: S
authors.lastname: Nechaev
authors.forename: Vikas
authors.initials: V
authors.lastname: Jain
authors.forename: E Peter
authors.initials: EP
authors.lastname: Geiduschek
authors.forename: Ann
authors.initials: A
authors.lastname: Hochschild
authors.forename: Seth A
authors.initials: SA
authors.lastname: Darst
mesh_terms: D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000737:chemistry*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000737:chemistry; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D021122:Protein Subunits; D012808:Sigma Factor; D015534:Trans-Activators; D014764:Viral Proteins; C085859:gene 33 protein, Enterobacteria phage T4; C540081:rpoB protein, E coli; D012321:DNA-Directed RNA Polymerases