T7 RNA Polymerase

T7 RNA Polymerase Initiation Complex

spinqualitylabelsall models Promoter bound polymerase Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D T7 RNA polymerase binds and melts into dsDNA, by recognizing the upstream duplex region of the promoter (-17 to -5), and then melting a bubble (-4 to about +3), within the larger duplex. The duplex promoter domain binds primarily to the N-terminal domain of the enzyme, with the exception of the (C-terminal domain) "specificity loop." It is the combination of the N-terminal domain, with the positioned specificity loop, that forms the specific binding surface. The enzyme then binds the first two substrate NTP's, as directed by the template (typically two GTP's, encoded by CC in the template strand). A phosphoryl transfer reaction occurs to form the product dinucleotide (pppGpG). At this point, the complex is in the pre-translocated state and to add the next base, the enzyme must translocate forward along the DNA (or equivalently, the RNA/DNA slides backwards), forming the post-translocated state. In the latter state (only) the active site now accommodates binding of the next NTP to the (+3) template base. Structural highlights This is a sample scene created with SAT to color by Group, and another to make a transparent representation of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.

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Craig T Martin, Karsten Theis, Jaime Prilusky, Ann Taylor, Michal Harel