Organization of an activator-bound RNA polymerase holoenzyme.
Transcription initiation involves the conversion from closed promoter complexes, comprising RNA polymerase (RNAP) and double-stranded promoter DNA, to open complexes, in which the enzyme is able to access the DNA template in a single-stranded form. The complex between bacterial RNAP and its major variant sigma factor sigma(54) remains as a closed complex until ATP hydrolysis-dependent remodeling by activator proteins occurs. This remodeling facilitates DNA melting and allows the transition to the open complex. Here we present cryoelectron microscopy reconstructions of bacterial RNAP in complex with sigma(54) alone, and of RNAP-sigma(54) with an AAA+ activator. Together with photo-crosslinking data that establish the location of promoter DNA within the complexes, we explain why the RNAP-sigma(54) closed complex is unable to access the DNA template and propose how the structural changes induced by activator binding can initiate conformational changes that ultimately result in formation of the open complex.
Bose
Daniel
D
Division of Molecular Biosciences, Centre for Structural Biology, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK.
Pape
Tillmann
T
Burrows
Patricia C
PC
Rappas
Mathieu
M
Wigneshweraraj
Siva R
SR
Buck
Martin
M
Zhang
Xiaodong
X
D001105:Archaea / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism*; D004789:Enzyme Activation; D020035:Holoenzymes / Q000235:genetics / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D051877:RNA Polymerase Sigma 54 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013698:Templates, Genetic
D019843:Archaeal Proteins; D001426:Bacterial Proteins; D020035:Holoenzymes; D021122:Protein Subunits; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54