Common structural features of nucleic acid polymerases.
Structures of multisubunit RNA polymerases strongly differ from the many known structures of single subunit DNA and RNA polymerases. However, in functional complexes of these diverse enzymes, nucleic acids take a similar course through the active center. This finding allows superposition of diverse polymerases and reveals features that are functionally equivalent. The entering DNA duplex is bent by almost 90 degrees with respect to the exiting template-product duplex. At the point of bending, a dramatic twist between subsequent DNA template bases aligns the "coding" base with the binding site for the incoming nucleoside triphosphate (NTP). The NTP enters through an opening that is found in all polymerases, and, in most cases, binds between an alpha-helix and two catalytic metal ions. Subsequent phosphodiester bond formation adds a new base pair to the exiting template-product duplex, which is always bound from the minor groove side. All polymerases may undergo "induced fit" upon nucleic acid binding, but the underlying conformational changes differ.
Cramer
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Institute of Biochemistry, Gene Center, University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany. cramer@LMB.uni-muenchen.de
D002384:Catalysis; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009696:Nucleic Acids / Q000378:metabolism; D012313:RNA / Q000737:chemistry*; D012316:RNA Nucleotidyltransferases / Q000737:chemistry*
D009696:Nucleic Acids; D012313:RNA; D012316:RNA Nucleotidyltransferases; D012321:DNA-Directed RNA Polymerases